APPLICATIONS OF RING COUNTER AND COUNTER DECODER.
COUNTER with DECODERy It can be used in the place of ring
counter..ie.,it can also
generate timing signals y The timing signals when enabled by
clock pulses will provide multiphase clock pulses eg: To AND with
CP the output will generate CP at one fourth frequency that of
master clock.
RING COUNTER applicationsUsed for generating timing signals for
control unit in computers operating in parallel mode
Used as a stepper motor controller
HARDWIRE CONTROL UNIT
One flip-flop per state method
Sequence register and decoder method
4 TYPES PLA control Micro program control
ONE FLIPFLOP PER STATE METHODy Uses Only flipflop per state and
others are cleared y A single bit is made to propagate from one
flipflop to the
other under the control of decision logic y If the control ckt
does not need external inputs for its sequencing, the ckt reduces
to a shift register with a single bit shifted from one position to
next. For this reason, this method is also called RING COUNTER
CONTROLLER
SEQUENCE REGISTER AND DECODERy This method uses a register to
sequence the control states the
register is decoded to provide one output per each state y If
the control ckt does not need external inputs , the sequence
register reduces to counter that continously sequences. For this
reason, this method is called as COUNTER DECODER METHOD
I.R OPCODE LDE STE ADD decoder SUB MBA JMP JN
RING COUNTER T T 5 4 T T 3 2 T T 1 0 CLK
CONTROL MATRIX
HALT
NEG.FLAG CONTROL SIGNALS
WORKING:y The ring counter provides a sequence of six
consecutive
active signals y The instruction decoder takes its input from
the op-code field and activates only one of 8 output lines y Each
line corresponds to one of the instructions in the computer
instruction set y The control matrix receives input from
instruction decoder and ring counter and provides the proper
sequence of control signals
y Eg: LM=To + T3 *LDA + T3*STA y INSTRUCTION SET y
IP = T2 W = T5*STA LP = T3*JMP + T3*NF*JN LD = T4*STA LA =
T5*LDA + T3*ADD + T3*SUB EA = T4*STA + T3*MBA EP = T0 S = T3*SUB A
= T3*ADD LI = T2 LM = T0 + T3*LDA + T3*STA ED = T2 + T5*LDA R = T1
+ T4*LDA EU = T3*ADD+T3*SUB EI = T3*LDA + T3*STA + T3*JMP +
T3*NF*JN LB = T3*MBA
