MK68901

December1988

MULTIFUNCTION PERIPHERAL

. 8 INPUT/OUTPUT PINS Individually programmable direction Individual interrupt source capability

-

Programmable edge selection. 16 SOURCE INTERRUPT CONTROLLER

8 Internal sources 8 External sources Individual source enable Individual source masking Programmable interrupt service modes

-

Polling-

Vector generation-

Optional In-service status Daisy chaining capability

. FOUR TIMERS WITH INDIVIDUALLY PRO-GRAMMABLE PRESCALING Two multimode timers

-

Delay mode-

Pulse width measurement mode-

Event counter mode Two delay mode timers Independent clock input Time out output option

. SINGLE CHANNEL USART Full Duplex Asynchronous to 65 kbps Byte synchronous to 1 Mbps Internal/External baud rate generation DMA handshake signals Modem control Loop back mode

. 68000 BUS COMPATIBLE

. 48 PIN DIP OR 52 PIN PLCC

Figure 1 : Pin connections.

DESCRIPTIONThe MK68901 MFP (Multi-Function Peripheral) is acombination of many of the necessary peripheralfunctions in a microprocessor system.Included are :

Eight parallel I/O linesInterrrupt controller for 16 sourcesFour timersSingle channel full duplex USART

The use of the MFP in a system can significantly re-duce chip count, thereby reducing system cost. TheMFP is completely 68000 bus compatible, and 24 di-rectly addressable internal registers provide the ne-

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necessary control and status interface to the pro-grammer.The MFP is a derivative of the MK3801 STI, a Z80family peripheral.

PIN DESCRIPTIONGND : GroundVCC : +5 volts ( 5%)CS : Chip Select (input, active, low). CS is u-

sed to select the MK68901 MFP for ac-cesses to the internal registers. CS andIACK must not be asserted at the sametime.

DS : Data Strobe (input, active low). DS is u-sed aspart of thechip select and interruptacknowledge functions.

R/W : Read/Write (input). R/W is the signalfrom the bus master indicating whetherthe current bus cycle is a Read (High) orWrite (Low) cycle.

DTACK : Data Transfer Acknowledge. (output, ac-tive low, tri-stateable) DTACK is used tosignal the bus master that data is ready,or that data has been accepted by theMK68901 MFP.

A1-A5 : Address Bus (inputs). The adress bus isused to adress one of the internal regis-ters during a read or write cycle.

D0-D7 : Data Bus (bi-directional, tri-stateable).The data bus is used to receive data fromor transmit data to one of the internal re-gisters during a read or write cycle. It isalso used to pass a vector during an in-terrupt acknowledge cycle.

CLK : Clock (input). This input is used to pro-vide the internal timing for the MK68901MFP.

RESET : Device reset. (input, active low). Resetdisables the USART receiver and trans-mitter, stops all timers and forces the ti-mer outputs low, disables all interruptchannels and clears any pending inter-rupts. The General Purpose Interrupt/I/Olines will be placed in the tri-state inputmode. All internal registers (except the ti-mer, USART data registers, and transmitstatus register) will be cleared.

INTR : Interrupt Request (output, active low, o-pen drain). INTR is asserted when theMK68901 MFP is requesting an interrupt.INTR is negated during an interrupt ac-

knowledge cycle or by clearing the pen-ding interrupt(s) through software.

IACK : Interrupt Acknowledge (input, activelow). IACK is used tosignal the MK68901MFP that the CPU is acknowledging aninterrupt. CS and IACk must not be as-serted at the same time.

IEI : Interrupt Enable In (input, active low). IEIis used to signal the MK68901 MFP thatno higher priority device is requesting in-terrupt service.

IEO : Interrupt Enable Out (output, active low).IEO is used to signal lower priority peri-pherals that neither the MK68901 MFPnor another higher priority peripheral isrequesting interrupt service.

10-17 : General Purpose Interrupt I/O lines.These lines may be used as interrupt in-puts and/or I/O lines. When used as in-terrupt inputs, their active edge is pro-grammable. A data direction register is u-sed to define which lines are to be Hi-Zinputs and which lines are to be push-pullTTL compatible outputs.

SO : Serial Output. This is the output of the U-SART transmitter.

SI : Serial Input. This is the input to the U-SART receiver.

RC : Receiver Clock. This input controls theserial bit rate of the USART receiver.

TC : Transmitter Clock. This input controls theserial bit rate of the USART transmitter.

RR : Receiver Ready. (output, active low)DMA output for receiver, which reflectsthe status of Buffer Full in port number15.

TR : Transmitter Ready. (output, active low)DMA output for transmitter, which re-flects the status of Buffer Empty in portnumber 16.

TAO,TBO,TCO,TDO:

Timer Outputs. Each of the four timershas an output which can produce asquare wave. The output will changestates each timer cycle ; thus one full pe-riod of the timer out signal is equal to twotimer cycles. TAO or TBO can be reset(logic O) by a write to TACR, or TBCRrespectively.

XTAL1,XTAL2 :

Timer Clock inputs. A crystal can beconnected between XTAL1 and XTAL2,or XTAL1 can be driven with a TTL levelclock. When driving XTAL1 with a TTL le-

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vel clock, XTAL2 must be allowed to float.Whenusing a crystal, external capacitorsare required. See figure 33. All chip ac-cesses are independent of the timerclock.

TAI,TBI : Timer A, B inputs. Used whenrunning the

timers in the event count or the pulsewidth measurement mode. The interruptchannels associated with 14 and 13 areused for TAI and TBI, respectively. Thus,when running a timer in the pulse width

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Figure 4 : Register Map.

Address Port N. Abbreviation Register Name012

GPIPAERDDR

GENERAL PURPOSE I/OACTIVE EDGE REGISTERDATA DIRECTION REGISTER

3456789AB

IERAIERBIPRAIPRBISRAISRBIMRAIMRB

VR

INTERRUPT ENABLE REGISTER AINTERRUPT ENABLE REGISTER BINTERRUPT PENDING REGISTER AINTERRUPT PENDING REGISTER BINTERRUPT IN-SERVICE REGISTER AINTERRUPT IN-SERVICE REGISTER BINTERRUPT MASK REGISTER AINTERRUPT MASK REGISTER BVECTOR REGISTER

CDEF101112

TACRTBCR

TCDCRTADRTBDRTCDRTDDR

TIMER A CONTROL REGISTERTIMER B CONTROL REGISTERTIMERS C AND D CONTROL REGISTERTIMER A DATA REGISTERTIMER B DATA REGISTERTIMER C DATA REGISTERTIMER D DATA REGISTER

1314151617

SCRUCRRSRTSRUDR

SYNC CHARACTER REGISTERUSART CONTROL REGISTERRECEIVER STATUS REGISTERTRANSMITTER STATUS REGISTERUSART DATA REGISTER

INTERRUPTSThe General Purpose I/O-Interrupt Port (GPIP) pro-vides eight I/O lines that may be operated either asinputs or outputs under software control. In addition,each line may generate an interrupt in either a po-sitive going edge or a negative going edge of the in-put signal.The GPIP has three associated registers. One al-lows the programmer to specify the Active Edge foreach bit that will trigger an interrupt. Another registerspecifies the Data Direction (input or output) asso-ciated with each bit. The third register is the actualdata I/O register used to input or output data to theport. These three registers are illstrated in figure 5.The Active Edge Register (AER) allows each of theGeneral Purpose Interrupts to provide an interrupton either a 1-0 transition or a 0-1 transition. Writinga zero to the appropriate bit of the AER causes theassociated input to produce an interrupt on the 1-0transition. The edge bit is simply one input to an ex-clusive-or gate, with the other input coming from theinput buffer ant the output going to a 1-0 transitiondetector. Thus, depending upon the state of the in-put, writing the AER can cause an interrupt-produ-cing transition, which will cause an interrupt on theassociated channel, if that channel is enabled. One

would then normally configure the AER beforeenabling interrupts via IERA and IERB.Note : Changing the edge bit, with the interruptenabled, may cause an interrupt on that channel.The Data Direction Register (DDR) is used todefine10-17 as inputs or as outputs on a bit by bit basis.Writing a zero into a bit of the DDR causes the cor-responding Interrupt-I/O pin to be a Hi-Z input. Wri-ting a one into a bit of the DDR causes the cor-responding pin to be configured as a push-pull out-put. When data is written into the GPIP, those pinsdefined as inputs will remain in the Hi-Z state whilethose pins defined as outputs will assume the state(high or low) of their corresponding bit in the GPIP.When the GPIP is read, the data read will come di-rectly from the corresponding bit of the GPIPregisterfor all pins defined as output, while the data read onall pins defined as inputs will come from the inputbuffers.Each individual function in the MK68901 is providedwitha unique interrupt vector that is presented to thesystemduring the interrupt acknowledge cycle. Theinterrupt vector returned during the interrupt ac-knowledge cycle is shown in figure 6, while the vec-tor register is shown in figure 7.

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There are 16 vector addresses generated internallyby the MK68901, one for each of the 16 interruptchannels.The Interrupt Control Registers (figure 8) providecontrol of interrupt processing for all I/O facilities ofthe MK68901. These registers allow the program-

mer to enable or disable any or all of the 16 inter-rupts, providing masking for any interrupt, and pro-vide access to the pending and in-service status ofthe interrupt. Optional end-of-interrupt modes areavailable under software control. All the interruptsare prioritized as shown in figure 9.

Figure 5 : General Purpose I/O Registers.

Figure 6 : Interrupt Vector.

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Figure 7 : Vector Register.

Figure 8 : Interrupt Control Registers.

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Figure 9 : Interrupt Control Register DefinitionsPriority Channel Description

HIGHEST

LOWEST

1111111011011100101110101001100001110110010101000011001000010000

General Purpose Interrupt 7(I7)General Purpose Interrupt 6(I6)Timer AReceive Buffer FullReceive ErrorTransmit Buffer EmptyTransmit ErrorTimer BGeneral Purpose Interrupt 5(I5)General Purpose Interrupt 4(I4)Timer CTimer DGeneral Purpose Interrupt 3(I3)General Purpose Interrupt 2(I2)General Purpose Interrupt 1(I1)General Purpose Interrupt 0(I0)

Interrupts may be either polled or vectored. Eachchannel may be individual enabled or disabled bywriting a one or a zero in the appropriate bit of Inter-rupt Enable Registers (IERA, IERB - see figure 8 forall registers in this section). When disabled, an in-terrupt channel is completely inactive. Any internalor external action which would normally produce aninterrupt on thatchannel is ignored and any pendinginterrupt on that channel will be cleared by disablingthat channel. Disabling an interrupt channel has noeffect on the corresponding bit in Interrupt In-Ser-vice Registers (ISRA, ISRB) ; thus, if the In-serviceRegisters are used and an interrupt is in service onthat channel when the channel is disabled, it will re-main in service until cleared in the normal manner.IERA and IERB are also readable.When an interrupt is received on an enabled chan-nel, its corresponding bit in the pending register willbe set. When that channel is acknowledged it willpass its vector, and the corresponding bit in the In-terrupt Pending Register (IPRA or IRPB) will becleared. IPRA and IPRB are readable ; thus by pol-ling IPRA and IPRB, it can be determined whethera channel has a pending interrupt. IPRA and IPRBare also writeable and a pending interrupt can becleared without going through the acknowledge se-quence by writing a zero to the appropriate bit. Thisallows any one bit to be cleared, without altering anyother bits, simply by writing all ones except for thebit position to be cleared to IPRA or IPRB. Thus afully polled interrupt scheme is possible. Note : wri-ting a one to IPRA, IPRB has no effect on the inter-rupt pending register.

The interrupt mask registers (IMRA and IMRB) maybe used to block a channel from making an interruptrequest. Writing a zero into the corresponding bit ofthe mask register will still allow the channel to re-ceive an interrupt and latch it into its pending bit (ifthat channel is enabled), but will prevent that chan-nel from making an interrupt request. If that channelis causing an interrupt request at the time the cor-responding bit in the mask register is cleared, the re-quest will cease. If no other channel is making a re-quest, INTR will go inactive. If the mask bit is re-en-abled, any pending interrupt is now free to resumeits request unless blocked by a higher priority re-quest for service. IMRAand IMRB are also readable. A conceptual circuit of an interrupt channel isshown in figure 10.

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Figure 10 : A Conceptual Circuit of an Interrupt Channel.

There are two end-of-interrupt modes : the automat-ic end-of-interrupt mode and thesoftware end-of-in-terrupt mode. The mode is selected by writing a oneor a zero to the S bit of the Vector Register (VR). Ifthe S bit of the VR is a one, all channels operate inthe software end-of-interrupt mode. If the S bit is azero, all channels operate in the automatic end-of-interrupt mode, and a reset is held on all in-servicebits. In the automatic end-of-interrupt mode, thepending bit is cleared when that channel passes itsvector. At that point, no further history of that inter-rupt remains in the MK68901 MFP. In the softwareend-of-interrupt mode, the in-service bit is set andthe pending bit is cleared when the channel passesits vector. With the in-service bit set, no lower prioritychannel is allowed to request an interrupt or to passits vector during an acknowledge sequence ; how-ever, a lower priority channel may still receive an in-terrupt and latch it into the pending bit. A higher prio-rity channel may still request an interrupt and be ac-

knowledged. The in-service bit of a particular chan-nel may be cleared by writing a zero to the corre-sponding bit in ISRA or ISRB. Typically, this will bedone at the conclusion of the interrupt routine justbefore the return. Thus no lower priority channel willbe allowed to request service until the higher prioritychannel is complete, while channels of still higherpriority will be allowed to request service. While thein-service bit is set, a second interrupt on that chan-nel maybe received and latched into the pendingbit,though no service request will be made in re-sponse to the second interrupt until the in-service bitis cleared. ISRA and ISRB may be read at any time.Only a zero may be written into any bit of ISRA andISRB ; thus the in-service bits maybe cleared insoft-ware but cannot be set in software. This allows anyone bit to be cleared, without altering any other bits,simply by writing all ones except for the bit positionto be cleared to ISRA or ISRB, as with IPRA andIPRB.

Figure 11 a : A Conceptual Circuit of the MK68901 MFP Daisy Chaining.

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Figure 11 b : Daisy Chaining.

Each interrupt channel responds with a discrete 8-bit vector when acknowledged. The upper four bitsof the vector are set by writing the upper four bits ofthe VR. The four low order bits (bit 3-bit 0) are ge-nerated by the interrupting channel.To acknowledge an interrupt, IACK goes low, the IEIinput must go low (or be tied low) and the MK68901MFP must have an acknowledgeable interrupt pen-ding. The Daisy Chaining capability (figure 11) re-quires that all parts in a chainhave acommon IACK.When the common IACK goes low, all parts freezeand prioritize interrupts in parallel. Then priority ispassed down the chain, via IEI and IEO, until a partwhich has a pending interrupt is reached. The partwith the pending interrupt, passes a vector,does notpropagate IEO, and generates DTACK.Figure 9 describes the 16 prioritized interrupt chan-nels. As chown, General Purpose Interrupt 7 has thehighest priority, while General Purpose Interrupt 0 isassigned the lowest priority. Each of these channelsmay be reprioritized, in effect, by selectively ma-sking interrupts under software control. The binarynumbers under channel correspond to the modi-fied bits IV3, IV2, IV1 and IV0, respectively, of theInterrupt Vector for each channel (see figure 6).Each channel has an enable bit contained in IERAor IERB, a pending latch contained in IPRA or IPRB,a mask bit contained in IMRA or IMRB, and an inservice latch contained in ISRA or ISRB. Additional-ly, the eight General Purpose Interrupts each havean edge bit contained in the Active Edge Register(AER), a bit to define the line as input or outputcontained in the Data Direction Register (DDR) and

an I/O bit in the General Purpose Interrupt-I/O Port(GPIP).

TIMERSThere are four timers on the MK68901 MFP. Two ofthe timers (Timer A and Timer B) are full function ti-mers which can perform the basic delay functionand can also perform event counting, pulse widthmeasurement, and waveform generation. The othertwo timers (Timer C and Timer D) are delay timersonly. One or both of these timers canbe used to sup-ply the baud rate clocks for the USART. All timersare prescaler/counter timers with a common inde-pendent clock input (XTAL1, XTAL2). In addition, alltimers have a time-out output, function that toggleseach time the timer times out.The four timers are programmed via three TimerControl Registers and four Timer DataRegisters. Ti-mers A and B are controlled by the control registersTACR and TBCR, respectively (see figure 12), andby the data registers TADR and TBDR (figure 13).Timers C and D are controlled by the control registerTCDCR (see figure 14) and two data registersTCDR and TDDR. Bits in the control registers allowthe selection of operational mode, prescale, andcontrol white the data registers are used to read thetimer or write into the time constant register. TimerA and B input pins TAI and TBI, are used for the e-vent and pulse width modes for timers A and B.With the timer stopped, no counting can occur. Thetimer contents will remain unaltered while the timeris stopped (unless reloaded by writing the Timer Da-ta Register), but any residual count in the prescalerwill be lost.

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In the delay mode, the prescaler is always active.A count pulse will be applied to the main timer uniteach time the prescribed number of timer clock cy-cles has elapsed. Thus, if the prescaler is program-med to divide by ten, a count pulse will be appliedto the main counter every ten cycles of the timerclock.Each time acount pulse is applied to the main coun-ter, it will decrement its contents. The main counteris initially loaded by writing to the Timer Data Regis-ter. Each count pulse will cause the current count todecrement. When the timer has decremented downto 01 , the next count pulse will not cause it to de-crement to 00. Instead, the next count pulse willcause the timer to be reloaded from the Timer DataRegister.Additionally, a Time out pulse will be pro-duced. This Time Out pulse is coupled to the timerinterrupt channel, and, if that channel is enabled, aninterrupt will be produced. The Time Out pulse is al-so coupled to the timer output pin and will cause thepin to change states. The output will remain in thisnew stateuntil the next Time Out pulse occurs. Thusthe output will complete one full cycle for each twoTime Out pulses.If, for example, the prescaler were programmed todivide by ten, and the Timer Data Register were loa-

ded with 100 (decimal), the main counter would de-crement once for every ten cycles of the timer clock.A Time Out pulse will occur (hence aninterrupt if thatchannel is enabled) every 1000 cycles of the timerclock, and the timer output will complete one full cy-cle every 2000 cycles of the timer clock.The main counter is an 8-bit binary down counter. Itmay be read at any time by reading the Timer DataRegister. The information read is the informationlast clocked into the timer read register when the DSpin had last gone high prior to thecurrent read cycle.When written,data is loaded into the Timer Data Re-gister, and the main counter, if the timer is stopped.If the Timer Data Register is written while the timeris running, the new word is not loaded into the timeruntil it counts through H01. However, if the timeris written while it is counting through H01, an inde-terminate value will be written into the timer constantregister. This may be circumvented by ensuring thatthe data register is not written when the count isH01.If the main counter is loaded with 01, a Time OutPulse will occur every time the prescaler presentsa count pulse to the main counter. If loaded with00, a Time Out pulse will occur every 256 countpulses.

Figure 12 : Timer A and B Control Registers.

* Unused bits : read as zeros.

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Figure 13 : Timer Data Registers (A, B, C, and D).

Figure 14 : Timer C and D Register.

* Unused bi ts : read as zeros.

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Figure 15 : A Conceptual Circuit of the MFP Timers in the Pulse Width Measurement Mode.

Changing the prescale value with the timer runningcan cause the first Time Out pulse to occur at an in-determinate time, (no less than one nor more than200 timer clock cycles times the number in the timeconstant register), but subsequent Time Out pulseswill then occur at the correct interval.In addition to the delay mode described above, Ti-mers A and B can also function in the Pulse WidthMeasurement mode or in the Event Count mode. Ineither of these two modes, an auxiliary control signalis required. The auxiliary control input for Timer A isTAI, and for Timer B,TBI is used. The interrupt chan-nels associated with 14 and 13 are used for TAIandTBI, respectively, in Pulse Width mode. See Figure15.The pulse width measurement mode functionsmuch like the delay mode. However, in this mode,the auxiliary control signal on TAI or TBI acts as anenable to the timer. When the control signal on TAIor TBI is inactive, the timer will be stopped. When itis active, the prescaler andmain counter are allowedto run. Thus the width of the active pulse on TAI orTBI is determined by the number of timer countswhich occur while the pulse allows the timer to run.The active state of the signal on TAI or TBI is de-pendent upon the associated Interrupt Channelsedge bit (GPIP 4 for TAI and GPIP 3 for TBI : seeActive Edge Register in figure 5). If the edge bit as-

sociated with the TAI or TBI input is a one, it will beactive high ; thus the timer will be allowed to runwhen the input is at a high level. If the edge bit is azero, the TAI or TBI input will be active low. As pre-viously stated, the interrupt channel (13 or 14) as-sociated with the input still functions when the timeris used in the pulse width measurement mode. How-ever, if the timer is programmed for the pulse widthmeasurement mode, the interrupt caused by tran-si-tions on the associated TAI or TBI input will occur onthe opposite transition.For example, if the edge bit associated with the TAIinput (AER-GPIP 4) is as one, an interrupt wouldnormally be generated on the 0-1 transition of the 14input signal. If the timer associated with this input(Timer A) is placed in the pulse width measurementmode, the interrupt will occur on the 1-0 tran-sitionof the TAI signal instead. Because the edge bit(AER-GPIP 4) is a one, Timer A will be allowed tocount while the input is high. When the TAI inputmakes the high to low transition, Timer A will stop,and it is at this point that the interrupt will occur (as-suming that the channel is enabled). This allows theinterrupt to signal the CPU that the pulse being mea-sured has terminated ; thus Timer A may now beread to determine the pulse width. (Again note that13 and 14 may still be used for I/O when the timeris in the pulse width measurement mode). If Timer

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A is reprogrammed for another mode, interrupts willagain occur on the transition, as normally defined bythe edge bit. Note that, like changing the edge bit,placing the timer into or taking it out of the pulsewidth mode can produce a transition on the signalto the interrupt channel and may cause an interrupt.If measuring consecutive pulses, it is obvious thatone must read the contents of the timer and then rei-nitialize the main counter by writing to the timer dataregister. If the timer data register is written while thepulse is going to the active state, the write operationmay result in an indeterminate value being writteninto the main counter. If the timer is written after thepulse goes active, the timer counts from the pre-vious contents, and when it counts through H01,the correct value is written into the timer. The pulsewidth then includes counts from before the timerwas reloaded.In the event count mode, the prescaler is disabled.Each time the control input on TAI or TBi makes anactive transition as defined by the associated Inter-rupt Channels edge bit, a count pulse will be gene-rated, and the main counter will decrement. In all o-ther respects, the timer functions as previously des-cribed. Altering the edge bit while the timer is in theevent count mode can produce a count pulse. Theinterrupt channel associated with the input (I3 for I4for TAI) is allowed to function normally. To counttransitions reliably, the input must remain in eachstate (1/O) for a length of time equal to four periodsof the timer clock ; thus signals of a frequency up toone fourth of the timer clock can be counted.The manner in which the timer output pins togglestates has previously been described. All timer out-puts will be forced low by a device RESET. The out-put associated with Timers A and B will toggle oneach Time Out pulse regardless of the mode the ti-mers are programmed to. In addition, the outputsfrom Timers A and B can be forced low at any timeby writing a 1 to the reset location in TACR and

TBCR, respectively. The output will be forced to thelow state during the WRITE operation, and at theconclusion of the operation, the output will again befree to toggle each time a Time Out pulse occurs.This feature will allow waveform generation.During reset, the Timer Data Registers and the maincounters are not reset. Also, if using the reset optionon Timers A or B, one must make sure to keep theother bits in the correct state so as not to affect theoperation of Timers A and B.

USARTSerial Communication is provided by a full-duplexdouble-buffered USART, which is capable of eitherasynchronous or synchronous operation. Variableword length and start/stop bit configurations areavailable under software control for asynchronousoperation. For synchronous operation, a Sync Wordis provided to establish synchronization during re-ceive operations. The Sync Word will also be repea-tedly transmitted when no other data is available fortransmission. Moreover, the MK68901 allows strip-ping of all Sync Words received in synchronous o-peration. The handshake control lines RR (ReceiverReady) and TR (Transmitter Ready) allow DMA o-peration. Separate receive and transmit clocks areavailable, and separate receive and transmit statusand data bytes allow independent operation of thetransmit and receive sections.The USART is provided with three Control/StatusRegisters and a Data Register. The USART DataRegister form is illustrated in figure 16. The pro-grammer may specify operational parameters fortheUSART via the Control Register, as shown in fig-ure 17. Status of both the Receiver and Transmittersections is accessed by means of the twoStatus Re-gisters, as shown in figures 18 and 19. Data writtento the Data Register is passed to the transmitter,while reading the Data Register will access data re-ceived by the USART.

Figure 16 : USART Data Register.

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16/ 1 : When this bit is zero, data will be clockedinto and out of the receiver and transmit-ter at the frequency of their respectiveclocks. When this bit is loaded with aone,data will be clocked into and out of the re-ceiver and transmitter at one sixteenththe frequency of their respective clocks.Additionally, when placed in the divide bysixteenmode, the receiver data transitionresynchronization logic will be enabled.

WL0-WL1 :Word Length Control. These two bits setthe length of the data word (exclusive ofstart bits, stop bits, and parity bits as fol-lows:

ST0-ST1 : Start/stop bit control (format control).These two bits set the format as follows

:

PARITY : Parity Enabled. When set (1), parity willbe checked by the receiver, parity will becalculated, and a parity bit will be insertedby the transmitter. When cleared (0) noparity check will be made and no parity bitwill be inserted for transmission.

For a word length of 8 the MFP calculatesthe parity and appends it when transmit-ting a sync character. For shorterlengths, the parity must be stored in theSync Character Register (SCR) alongwith the sync character.

E/O : Even-Odd. When set (1), even paritywill be used if parity is enabled. Whencleared (0), odd parity will be used if pa-rity is enabled.

Note that the synchronous or asynchronous formatmaybe selected independently of a 1or 16clock.Thus it is possible to clock data synchronously intothe device but still use start and stop bits. In thismode, all normal asynchronous format features stillapply. Data will be shifted in after a start bit is en-countered, and a stop bit will be checked to deter-mine proper framing. If a transmit underrun condi-tion occurs, the output will be placed in a markingstate, etc. It is conversely possible to clock data inasynchronously using a synchronous format. Thereis data transition detection logic built into the receiveclock circuitry which will re-synchronize the internalshift clock on each data transition so that, with suf-ficienty frequent data transitions, startbitsare not re-quired. In this mode, all other common synchronousfeatures function normally. This re-synchronizationlogic is only active in 16 clock mode.

RECEIVERThe receiver section of the USART is configured bythe UCR as previously described. The status of thereceiver can be determined by reading and writingto the Receiver Status Register (RSR). The RSR isconfigured as follows :

Figure 17 : USART Control Register (UCR).

WL1 WL0 Word Length0011

0101

8 Bits7 Bits6 Bits5 Bits

ST1 ST0 Start Bits StopBits Format00

11

0101

0111

01

11/22

SYNCASYNCASYNCASYNC

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Figure 18 : Receiver Status Register (RSR).

BF : Buffer Full. This bit is set when the inco-ming word is transferred to the receivebuffer. The bit is cleared when the re-ceive buffer is read by reading the UDR.This bit of the RSR is read only.

OE : Overrun Error. This flag is set if the inco-ming word is completely received anddue tobe tranferred to the receive buf-fer,but the last word in the receive buf-ferhasnot yet been read. When this conditionoccurs, the word in the receive buffer isnot overwritten by the new word. Notethat the status flags always reflect thestatus of the data word currently in there-ceive buffer. As such, the OE flag is notactually set until the good word currentlyin the buffer has been read. The interruptassociated with this error will also not begenerated unti the old word in the receivebuffer has been read.OE flag is cleared by reading the receiverstatus register, and new data words can-not be shifted to the receive buffer untilthis is done.

PE : Parity Error. This flag is set if the word re-ceived has a parity error. The flag is setwhen the received word is tranferredfrom the shift register to the receive buf-fer if the error condition exists. The flag iscleared when the next word which doesnot have a parity error is tranferred to thereceive buffer.

FE : Frame Error. This flag only applies to theasynchronous format. A frame error isdefined as a non-zero data word which isnot followed by a stop bit. Like the PEflag, the FE flag is set or cleared when aword is transferred to the receive buffer.

F/S : Found/Search. This combination controlbit and flag bit is only used with the syn-chronous format. It can be set or clearedbywriting to this bit of the RSR.Whenthisbit is cleared, the receiver is placed in thesearch mode. In this mode, a bit by bitcomparison of the incoming data to the

character in the Sync Character Register(SCR) is made. The word length counteris disabled. When a match is found, thisbit will be set automatically, and the wordlength counter will start as sync has notbeen achieved. An interrupt will be gene-rated on the receive error channel whenthe match occurs. The word just shiftedin will, or necessity, be equal to the synccharacter, and it will not be transferred tothe receive buffer.

B : Break. This flag is used only when the a-synchronous format is selected. This flagwill be setwhen an all zero data word, fol-lowed by no stop bit, is received. The flagwill stay set until both a non-zero bit is re-ceived and the RSR has been read atleast once since the flag was set. Breakindication will not occur if thereceive buff-er is full.

M/CIP : Match/Character in Progress. If the syn-chronous format is selected, this flag isthe Match flag. It will be set each time theword transferred to the receive buffermatches the sync character. It will be re-set each time the word transferred to thereceive buffer does not match the synccharacter. If the asynchronous format isselected, this flag represents Characterin Progress. It will be set upon a start bitdetect and cleared at the end of the word.

SS : Sync Strip Enable. If this bit is set to aone, data words that match the synccharacter will not be loaded into the re-ceive buffer, and no buffer full signal willbe generated.

RE : Receiver Enable. This control bit is usedto enable or disable the receiver. If a zerois written to this bit of the RSR, the recei-ver will turn off immediately. All flags in-cluding the F/S bit will be cleared. If a oneis written to this bit, normal receiver ope-ration is enabled. The receive clock hasto be running before the receiver is en-abled.

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There are two interrupt channels associated with thereceiver. One channel is used for the normal BufferFull condition, while the other channel is used whe-never an error condition occurs. Only one interruptis generated per word received, but dedicating twochannels allows separate vectors : one for the nor-mal condition, and one for an error condition. If theerror channel is disabled, an interrupt will be gen-e-rated via the Butter Full Channel, whether the wordreceived is normal or in error. Those conditionswhich produce an interrupt via the error channelare : Overrun, Parity Error, Frame Error, SyncFound, and Break. If a received word has an errorassociated with it, and the error interrupt channel isenabled, an interrupt will occur on the error channelonly.Each time a word is transferred into the receive buf-fer, a corresponding set of flags is latched into theRSR. No flags (except CIP) are allowed to changeuntil the data word has been read from the receivebuffer. Reading the receive buffer allows a new dataword to be transferred to the receive buffer when itis received. Thus one should first read the RSR thenread the receive buffer (UDR) to ensure that theflags just read match the data word just read. If donein the reverse order, it is possible that subsequentto reading the data word from the receive buffer, butprior to reading the RSR, a new word may be recei-ved and transferred to the receive buffer and, withit, its associated flags latched into the RSR. Thus,when the RSR is read, those flags may actually cor-respond to a different data word. It is good practice,also to read the RSR prior to a data read as, whenan overrun error occurs, the receiver will not assem-ble new characters until the RSR has been read.As previously stated, when overrun occurs, the OEflag will not be set and the associated interrupt willnot be generated until the receive buffer has beenread. If a break occurs, and the receive buffer hasnot yet been read, only the B flag will be set (OE will

not be set). Again, this flag will not be set until thelast valid word has been read from the receive buf-fer. If the break condition ends and another wholedata word is received before the receive buffer isread, both the B and OE flags will be set once thereceive buffer is read.If a break occurs while the OE flag is set, the B flagwill also be set.A break generates an interrupt when the conditionoccurs and again when the condition ends. If thebreak condition ends before it is acknowledged byreading the RSR, the receiver error interrupt indica-ting end of break will be generated once the RSR isread.Anytime the asynchronous format is selected, startbit detection is enabled. New data is not shifted intothe shift register until a zero bit is detected. If a 16clock is selected, along with the asynchronous for-mat, false start bit detection is also enabled. Anytransition has to be stable for 3 positive going edgesof the receive clock to becalled a valid transition. Fora start bit to be good, a valid 0-1 transition must notoccur for 8 positive clock transitions after the initialvalid 1-0 transition.After a good start bit has been detected, valid tran-sitions in the data are checked for continously.When a valid transition is detected, the counter isforced tostate zero, andno more transition checkingis started until state four. At stateeight, the previousstate of the transition checking logic is clocked intothe receiver.As a result of this resynchronization logic, it is pos-sible to run with asynchronous clocks without startand stop bits if there are sufficient valid transitionsin the data stream. This logic also makes the unitmore tolerant of clock skew for normal asynchro-nous communications than a device which employsonly start bit synchronization.

Figure 19 : Transmitter Status Register (TSR).

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TRANSMITTERThe transmitter section of the USART is configuredas to format, word length, etc. by the UCR, as pre-viously described. The status of the transmitter canbe determined by reading or writing the TransmitterStatus Register (TSR). The TRSis configured as fol-lows :BE : Buffer Empty. This status bit is set when

the word in the transmit buffer is transfer-red to the output shift register and thusthe transmit buffer may be reloaded withthe next data word. The flag is clearedwhen the transmit buffer is reloaded. Thetransmit buffer is loaded by writing to theUDR.

UE : This bit is set when the last word hasbeen shifted out of the transmit shift re-gister before a new word has been loa-ded into the transmit buffer. It is not ne-cessary toclear this bit before loading theUDR.This bit may be cleared by either readingthe TSR or by disabling the transmitter.After the setting of the UE bit, one fulltransmitter clock cycle is required beforethis bit can be cleared by a read. The ti-ming in some systems may allow a readof the TSR before the required clock cy-cle has been completed. This would re-sult in the UE bit not being cleared untilthe following read. To avoid this problem,a dummy read of the TSR should be per-formed at the end of he UE service rou-tine.Only one underrun error may be genera-ted between loads of the UDR regardlessof the number of transmitter clock cyclesbetween UDR loads.

AT : Thisbit causes the receiver to beenabledat the end of the transmission of the lastword in the transmitter if the transmitterhas been disabled.

END : Endor Transmission. When the transmit-ter is turned off with a character still in theoutput shift register, transmission willcontinue until that character is shiftedout. Once it has cleared the output regis-ter, the END bit will be set. If no character

is being transmitted when the transmitteris disabled, the transmitter will stop at thenext rising edge of the internal shift clock,and END will immediately be set. TheEND bit is cleared by re-enabling thetransmitter.

B : Break. This control bit will cause a breakto be transmitted. Whena 1 is written tothe B bit of the TSR,a break will be trans-mitted upon completion of the character(if any) currently being transmitted. Abreak will continue to be transmitted untilthe B bit is cleared by writing a 0 tot hisbit of the TSR. At that time, normal trans-mission will resume. The B bit has nofunction in the synchronous format. Set-ting the B bit to a one keeps the BE bitfrom being set to a one. So, if there werea word in the buffer at the start of break,it would remain there until the end ofbreak, at which time it would be transmit-ted (if the transmitter is still enabled). Ifthe buffer were not full at the start ofbreak, it could be written at any time du-ring the break. If the buffer is empty at theend of break, the underrun flag will be set(unless the transmitter is disabled).The BREAK bit cannot be set until thetransmitter has been enabled and thetransmitter has had sufficient time (oneclock cycle) to perform the internal resetand initialization functions.

H,L : High and Low. These two control bits areused to configure the transmitter output,when the transmitter is disabled, as fol-lows :H L Output State0 0 Hi-Z0 1 Low (0)1 0 High1 1 Loop-Connects transmitter output toreceiver input, and TC to Receiver Clock(RC and SI are not used ; they are bypas-sed internally). In loop back mode, trans-mitter output goes high when disabled.

Altering these two bits after Transmitter

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Figure 20 : SYNC Character Register.

Enable (XE) is set will alter the outputstate untilEND is false. These bits shouldbe set prior to enabling the transmitter.The state of these bits determine thestate of the first transmitted character af-ter the transmitter is enabled. If the highimpedance mode was selected prior tothe transmitter being enabled, the first bittransmitted is indeterminate.

XE : Transmitter Enable. This control bit is u-sed to enable or disable the transmitter.When set, the transmitter is enabled.When cleared, the transmitter will be di-sabled. If disabled, any word currently inthe output register will continue to betransmitted when XE is cleared, thetransmitter will turn off at the end of thebreak character boundary, and no end ofbreak stop bit is transmitted. The transmitclock must be running before the trans-mitter is enabled A one bit always pre-cedes the first word out of the transmitterafter the transmitter is enabled. There isa delay between the time the transmitterenable bit is written an when the transmit-ter reset goes low ; therefore, the H & Lbits should be written with the desiredstate prior to enabling the transmitter.

Like the receiver section, there are two separate in-terrupt channels associated with the transmitter.The buffer Empty condition causes an interrupt viaone channel, while the Underrun and END condi-tions will cause an interrupt via the second channel.When underrun occurs in the synchronous format,the character in the SCR will be transmitted until anew words is loaded into the transmit buffer. In theasynchronous format, a Mark will be continuouslytransmitted when underrun occurs.The transmit buffer can be loaded prior to enablingthe transmitter. When the transmitter is disabled,anycharacter currently in theprocess of being trans-mitted will continue to conclusion, but any characterin the transmit buffer will not be transmitted and willremain in the buffer. Thus no buffer empty interruptwill occur nor will the BE flag be ste. If the bufferwerealready empty, the BE flag would be set and wouldremain set. When the transmitter is disabled with acharacter in the output register but with no character

in the transmit buffer, an Underrun Error will not oc-cur when the character in progress concludes.Often it is necessary to send a break for some par-ticular period. To aid in timing a break transmission,a transmission, a transmit error interrupt will be ge-nerated at every normal character boundary timeduring a break transmission. The status register in-formation is unaffected by this error condition inter-rupt. It should be noted that an underrun error, if pre-sent, must be cleared from the TSR, and the inter-rupt pending register must be cleared of pendingtransmitter errors at the beginning of the breaktransmission or no interrupts will be generated at thecharacter boundary time.It the synchronous format is selected, the sync char-acter should be loaded into the Sync Character Re-gister (SCR) as shouwn in figure 20. This characteris compared to the received serial data during aSearch, and will be continuously transmitted duringan underrun condition.All flags in the RSR or TSR will continue to functionas described whether their associated interruptchannel is disabled or enabled. All interrupt chan-nels are edge triggered and, in many cases, it is theactual output ofa flag bit or flag bits which is coupledto the interrupt channel. thus, if a normal interruptproducing condition occurs while the interrupt chan-nel is disabled, no interrupt would be produced evenif the channel was subsequently enabled, becausea transition did not occur while the interrupt channelwas enabled. that particular flag bit would have tooccur a second time before another edge waspro-duced, causing an interrupt to be generated.Error conditions in the USART are determined bymonitoring the Receive Status Register and theTransmitter Status Register. These error conditionsare only valid for each word boundary and are notlatched. When executing block tranfers or data, it isnecessary to save any errors so that they can bechecked at the end of a block. In order to save errorconditions during data transfer, the MK68901 MFPinterrupt controller may be used by enabling error in-terrupt for the desired channel (Receive error orTransmit error) and by masking these bits off. Oncethe tranfer is complete, the Interrupt Pending Regis-ter can be polled, to determine the precence of apending error interrupt, and therefore an error.

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Unused bits in the sync character register are ze-roed out ; therefore, word length should be set upprior to writing the sync word in some cases. Syncword length is the word length plus one when parityis enabled. The user has to determine the parity ofthe syncword when the word length is not 8 bits. TheMK68901 MFP does not add a parity bit to the syncword if the word length is less than 8 bits. The extrabit in the sync word is transmitted as the parity bit.With a word length of eight, and parity selected, theparity bit for the sync word is computed an added onby the MK68901 MFP.

RR RECEIVER READYRR is asserted when the Buffer Full bit is set in theRSR unless a parity error or frame error is detectedby the receiver.

TR TRANSMITTER READYTR is asserted when the Buffer Empty bit is set in theTSR unless a break is currently being transmitted.

REGISTER ACCESSESAll register accesses are dependent on CLK asshown in the timing diagrams. To read a register, CSandDSmust beasserted, and R/W must byhigh. Theinternal read control signal is essentially the combi-nation of CS, DS, and RD/WR. Thus, the read ope-

ration will begin when CS and DS go active and willendwhen either CS or DSgoes inactive.Theaddressbus must be stable prior to the start of the operationandmust remain stable until theend of the operation.Unless a read operation or interrupt acknowledge cy-cle is in progress the data bus (D0-D7) will remain inthe tri-state condition.To write a register, CSand DSmust beasserted andR/W must be low. The address must be stable priorto the start of the operation and must remain stableuntil the end of the operation. After the MK68901 as-sertsDTACK, the CPU negates DS,. At this time, theMFP latches the data bus and writes the contents in-to the appropriate register. Also when DS is nega-ted, the MFP rescinds DTACK.For an interrupt acknowledge, the operation startswhen IACK goes low, and ends when IACK goeshigh. The data bus is tri-stated when either IACK orDS goes high.When CS or IACK are asserted the MFP starts aninternal cycle. DS is needed to enable the addressand data buffers. It is recommended taht CS andIACK be gated by DS so that DS is always presentwhenever an MFP bus cycle starts.

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D.C. CHARACTERISTICSTA = 0C to 70C ; VCC = + 5V 5% Unless Otherwise SpecifiedSymbol Parameter Test Condition Min. Max. Unit

VIH Input High Voltage 2.0 V CC + .3 VVIL Input Low Voltage 0.3 0.8 VVOH Output High Voltage (except DTACK) IOH = 120A 2.4 VVOL Output Low Voltage (except DTACK) IOL = 2.0mA 0.5 VIL L Power Supply Current Outputs Open 180 mAIL I Input Leakage Current VIN = 0 to VCC 10 A

IL OH Tri-state Output Leakage Current in Float VOUT = 2.4 to VCC 10 AIL OL Tri-state Output Leakage Current in Float VOUT = 0.5V 10 AIO H DTACK Output Source Current VOUT = 2.4 400 AIOL DTACK Output Sink Current VOUT = 0.5 5.3 mA

All voltages are referenced to ground.

CAPACITANCETA = 25C, f = 1MHz unmeasured pins returned to ground.Symbol Parameter Test Condition Max. Unit

CIN Input Capacitance Unmeasured pins returned toground

10 pFCO UT Tri-state Output Capacitance 10 pF

MK68901 ELECTRICAL SPECIFICATIONS PRELIMINARY

ABSOLUTE MAXIMUM RATINGSSymbol Parameter Value Unit

TA Temperature under Bias 25 to + 100 CTstg Storage Temperature 65 to + 150 CVI Voltage on Any Pin with Respect to Ground 0.3 to + 7 VPD Power Dissipation 1.5 W

Stresses above those l isted under Absolute Maximum Ratings may cause permanent damage to the device. This is a stressrating only and functional operation of the device at these or any other condition above those indicated in the operational sec-tions of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect re-l iability.

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AC ELECTRICAL CHARACTERISTICS (VCC = 5.0Vdc 5%, GND = 0Vdc, TA = 0C to 70C)Value

MK68901-4 MK68901-5Number CharacteristicMin. Max. Min. Max.

Unit Fig. Note

1 CS, DS Width High 50 35 ns 21,22 52 R/W, A1-A5 Valid to Falling CS (setup) 0 0 ns 21,223 Data Valid Prior to Falling CLK 280 0 ns 224 CS, IACK Valid to Falling Clock (setup) 50 45 ns 21-24 35 CLK Low to DTACK Low 220 180 ns 21,226 CS, DS or IACK High to DTACK High 60 55 ns 21-247 CS, DS or IACK High to DTACK Tri-state 100 95 ns 21-248 DTACK Low to Data Invalid (hold time) 0 0 ns 229 CS, DS or IACK High to Data Tri-state 50 50 ns 21,23,24

10 CS or DS High to R/W, A1-A5 Invalid (hold time) 0 0 ns 21,2211 Data Valid from CS Low 310 260 ns 21 3,612 Read Data Valid to DTACK Low (setup) 50 50 ns 2113 DTACK Low to DS, CS or IACK High (hold time) 0 0 ns 21-2314 IEI Low to Falling CLK (setup) 50 50 ns 23,2415 IEO Valid from Clock Low (delay) 180 180 ns 23 116 Data Valid from Clock Low (delay) 300 300 ns 2317 IEO Invalid from IACK High (delay) 150 150 ns 23, 2418 DTACK Low from Clock High (delay) 180 165 ns 23, 2419 IEO Valid from IEI Low (delay) 100 100 ns 24 120 Data Valid from IEI Low (delay) 220 220 ns 2421 Clock Cycle Time 250 1000 200 1000 ns 2122 Clock Width Low 110 90 ns 2123 Clock Width High 110 90 ns 2124 CS, IACK Inactive to Rising Clock (setup) 100 80 ns 21-23 4,525 I/O Minimum Active Pulse Width 100 100 ns 2526 IACK Width High 2 2 T CL K 23-24 227 I/O Data Valid from Rising CS or DS 450 450 ns 2628 Receiver Ready Delay from Rising RC 600 600 ns 2729 Transmitter Ready Delay from Rising TC 600 600 ns 2830 Timer Output Low from Rising Edge of CS or DS

(A & B) (reset T OUT) 450 450 ns 29 731 TOUT Valid from Internal Timeout 2 tCL K

+ 3002 tCL K+ 300 ns 29 2

32 Timer Clock Low Time 110 90 ns 29

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AC ELECTRICAL CHARACTERISTICS (continued)(VCC = 5.0Vdc 5%, GND = 0Vdc, TA = 0C to 70C)

ValueMK68901-4 MK68901-5Number CharacteristicMin. Max. Min. Max.

Unit Fig. Note

33 Timer Clock High Time 110 90 ns 2934 Timer Clock Cycle Time 250 1000 200 1000 ns 2935 RESET Low Time 2 1.8 s 3036 Delay to Falling INTR from External Interrupt

Active Transition 380 380 ns 25

37 Transmitter Internal Interrupt Delay from FallingEdge of TC 550 550 ns 28

38 Receiver Buffer Full Interrupt Transition Delayfrom Rising Edge of RC 800 800 ns 27

39 Receiver Error Interrupt Transition Delay fromFalling Edge of RC 800 800 ns 27

40 Serial in Set Up Time to Rising Edge of RC(divide by one only) 80 70 ns 27

41 Data Hold Time from Rising Edge of RC(divide by one only) 350 325 ns 27

42 Serial Output Data Valid from Falling Edge of TC(1) 440 420 ns 28

43 Transmitter Clock Low Time 500 450 ns 2844 Transmitter Clock High Time 500 450 ns 2845 Transmitter Clock Cycle Time 1.05 0.95 s 2846 Receiver Clock Low Time 500 450 ns 2747 Receiver Clock High Time 500 450 ns 2748 Receiver Clock Cycle Time 1.05 0.95 s 2749 CS, IACK, DS Width Low 80 80 T CL K 29 250 Serial Output Data Valid from Falling Edge of TC

(16) 490 370 ns 28Notes : 1. IEO only goes low if no acknowledgeable interrupt is

pending. If IEO goes low, DTACK and the data bus re-main tri-stated.

2. TCLK refers to the clock applied to the MFP CLK inputpin. tCLK refers to the timer clock signal, regardless ofwhether thatsignal comes from the XTAL 1/XTAL2crys-tal clock inputs or the TAI or TBI timer inputs.

3. If the setup time is not met, CS or IACK will not be reco-gnized until the next falling CLK.

4. If this setup time is met (for consecutive cycles), the mi-nimum hold-off time of one clock cycle will be obtained.If not met, the hold-off will be two clock cycles.

5. CS is latched internally, therefore if specs 1 and 24 aremet then CS may be reasserted before the rising clockandstill terminate the current bus cycle.The new buscy-cle will be delayed by the MK68901 until all appropriateinternal operations havecompleted.

6. Although CS and DTACK are synchronized with theclock, the data out during a read cycle is asynchronousto the clock, relying only on CS for timing.

7. Spec. 30 applies to timer outputs TAO and TBOonly.

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TIMER A.C. CHARACTERISTICSDefinitions :Error = Indicated Time Value - Actual Time Valuetpsc = tCLKx Prescale ValueInternal Timer Mode

Single Interval Error (free running) (note 2) 100ns Cumulative Internal Error 0 Error between Two Timer Reads (tpsc + 4tCLK) Start Timer to Stop Timer Error + (2tCLK + 100ns) to - (tpsc + 6tCLK + 100ns) Start Timer to Read Timer Error + 0 to (tpsc + 6tCLK + 400ns) Start Timer to Interrupt Request Error (note 3) - 2tCLK to (4tCLK + 800ns)

Notes : 1. Error may be cumulative if repetitively performed.2. Error with respect to TOUT or INT if note 3 is true.3. Assuming it is possible for the timer to make an interrupt request immediately.

PULSE WIDTH MEASUREMENT MODEMeasurement Accuracy (note 1) + 2tCLK to (tpsc + 4tCLK) Minimum Pulse Width 4tCLK

EVENT COUNTER MODEMinimum Active Time of TAI, TBI 4tCLK Minimum Inactive Time of TAI, TBI 4tCLK

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Figure 21 : Read Cycle.

Figure 22 : Write Cycle.

Note : CS and IACK must be a funct ion of DS.

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Figure 23 : Interrupt Acknowledge (IEI low).

Figure 24 : Interrupt Acknowledge Cycle (IEI high).

Note : CS and IACK must be a funct ion of DS.

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Figure 25 : Interrupt Timing.

Figure 26 : Port Timing.Note : Active edge is assumed to be the r ising edge.

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Figure 27 : Receiver Timing.

Figure 28 : Transmitter Timing.

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Figure 29 : Timer Timing.

Figure 30 : Reset Timing.

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Figure 31 : Typical Output. Figure 32 : INTR Test Load.

For all outputs exceptDTACKCL = 100pfRL = 20kR1 = 180

For DTACKCL = 130pfRL = 6kR1 = 470

Figure 33 : MK68901 MFP External Oscillator Components.

CRYSTAL PARAMETERS :Paral lel resonance, fundamental mode AT cutRS 150 (FR = 2.8 5.0MHz);RS 300 (FR = 2.0 2.7MHz)CL = 18pf ; CM = 0.02pf ; Ch = 5pf ; LM = 96mHFR (typ) = 2.4576MHz

MK68901 ORDER CODESPart Number PackageType Max. ClockFrequency TemperatureRange68901P0468901P0568901N0468901N0568901Q0468901Q05

Ceramic DIPCeramic DIPPlastic DIPPlastic DIPPlastic PLCCPlastic PLCC

4.0MHz5.0MHz4.0MHz5.0MHz4.0MHz5.0MHz

0 to 70C0 to 70C0 to 70C0 to 70C0 to 70C0 to 70C

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MK68901 48PIN PLASTIC DUALINLINE PACKAGE (N)

Millimeters InchesDim Min. Max. Min. Max.

A 61.468 62.738 2.420 2.470B 14.986 16.256 .590 .640C 13.462 13.97 .530 .550D 3.556 4064 .140 .160E 0.381 1.524 .015 .060F 3048 3.81 .120 .150G 1.524 2.286 .060 .090H 1.186 1.794 .090 .110J 15.24 17.78 .600 .700K 0.381 0.533 .015 .021L 0.203 0.305 .008 .012M 1.143 1.778 .045 .070

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MK68901 48PIN CERAMIC DUALINLINE PACKAGE (P)

InchesDim

Min. Max.A 2.376 2.424B 0.576 0.604C 0.120 0.160D 0.015 0.021F 0.030 0.055G 0.100 BSCJ 0.008 0.013K 0.100 0.165L 0.590 0.616M 0 10N 0.040 0.060

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MK68901 52PIN PLASTIC LEADED CHIP CARRIER (Q)

InchesDim

Min. Max.A .165 .180A1 .090 .130D .785 .795

D1 .750 .756D2 .690 .730E .785 .795E1 .750 .756E2 .690 .730H .042 .048J .042 .048K .013 .024L .008 .014M .026 .032

N/N1 .043 .048

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MK68901 PIN CONNECTIONSPLCC DIP FUNC. PLCC DIP FUNC. PLCC DIP FUNC.

123456789

101112131415161718

123456789

1011

1213141516

NCR/WA1A2A3A4A5TCSOSIRCVCCNCNC

TAOTBOTCOTDO

192021222324252627282930313233343536

1718

1920212223242526272829

303132

XTAL1XTAL2

NCTAITBI

RESETIOI1I2I3I4I5I6I7

NCTRRR

INTR

37383940414243444546474849505152

33343536373839404142434445464748

IEOIEI

CLKGNDD0D1D2D3D4D5D6D7

IACKDTACK

DSCS

Note : NC No Connection

Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes noresponsability for the consequences of use of such information nor for any infringement of patents or other rights ofthird parties which may result from its use. No license is granted by implication or otherwise under any patent orpatent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to changewithout notice. This publication supersedes and replaces all information previously supplied.SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices orsystems without the express written approval of SGS-THOMSON Microelectronics.

1994 SGS-THOMSON Microelectronics - All rights reserved.

Purchase of I2C Components by SGS-THOMSON Microelectronics conveys a license under the Philips I2C Patent.Rights to use these components in an I2C system is granted provided that the system conforms to the I2C Standard

Specification as defined by Philips.

SGS-THOMSON Microelectronics Group of Companies

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