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Accumulator Functions

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Overview of the Accumulator Functions

Instructions, that affect several Accumulators

TAK: Toggle (swap) the contents of ACCU1 and ACCU2

PUSH: Shifting the ACCU contents "upward"

POP: Shifting the ACCU contents "downward"

ENT: Shifting the ACCU contents "upward", without ACCU1

LEAVE: Shifting the ACCU contents "downward", without ACCU2

Arithmetic Instructions and Word Logic Instructions

Instructions, that only affect ACCU1

INC: Increment the contents of ACCU1-LL

DEC: Decrement the contents of ACCU1-LL

CAW: Reverse the order of the bytes in ACCU1-L

CAD: Reverse the order of the bytes in ACCU1

INVI, INVD: Forming the ones complement

NEGI, NEGD, NEGR: Forming the twos complement (Negation)

SLW, SLD, SRW, SRD, SSI, SSD: Shift the contents of ACCU1 word-by-word or doubleword-by-doubleword to the left or the right

RLD, RRD: Rotate the contents of ACCU1 to the left or to the right

RLDA, RRDA: Rotate the contents of ACCU1 to the left or to the rightvia the condition code bit CC1

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The Instruction TAK (Toggle ACCU1 and ACCU2)

S7-300:

S7-400:

ACCU1

ACCU2

V1

V2

V2

V1

before after

ACCU1

ACCU2

V1

V2

V3

V4

ACCU3

ACCU4

V2

V1

V3

V4

before after

TAK

TAK

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The Instructions PUSH and POP

S7-300:

ACCU1

ACCU2

V1

V2

V1

V1

before afterPUSH

S7-400:

ACCU1

ACCU2

ACCU3

ACCU4

V1

V2

V1

V2

V3

V4

V1

V1

V2

V3

before afterPUSH

V2

V2

before afterPOP

V1

V2

V3

V4

V2

V3

V4

V4

before afterPOP

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The Instructions ENT and LEAVE (only S7-400)

ENT:

LEAVE:

V1

V2

V3

V4

ACCU1

ACCU2

ACCU3

ACCU4

V1

V2

V2

V3

before after

V1

V2

V3

V4

ACCU1

ACCU2

ACCU3

ACCU4

V1

V3

V4

V4

before after

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Arithmetic Instructions

S7-300:

S7-400:

ACCU1

ACCU2

V1

V2

V2 op V1

V2

before after

ACCU1

ACCU2

V1

V2

V3

V4

ACCU3

ACCU4

V3

V4

V4

before after

op: +., -., *., /.

V2 op V1

op: +., -., *., /.

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Word Logic Instructions

S7-300:

S7-400:

ACCU1

ACCU2

V1

V2

V2 op V1

V2

before after

ACCU1

ACCU2

V1

V2

V3

V4

ACCU3

ACCU4

V2

V3

V4

before after

op: A.., O.., X..,

V2 op V1

op: A.., O.., X..,

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Change Instructions for ACCU1

CAW:

CAD:

V4 V3 V2 V1

ACCU1-HH ACCU1-HL ACCU1-LH ACCU1-LL

V4 V3 V1 V2

V4 V3 V2 V1

V1 V2 V3 V4

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Increment Instructions for ACCU1

ACCU1-HH ACCU1-HL ACCU1-LH ACCU1-LLINC :

V4 V3 V2 V1

V4 V3 V2 V1+

+

DEC :

V4 V3 V2 V1

V4 V3 V2 V1-

-

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Forming the Ones Complement

0 1 0 0 0 0 1 0 0 1 0 0 1 0 0 1 1 0 0 0 1 1 0 0 0 1 0 0 0 1 1 1

031

INVI (Ones Complement of ACCU1-L):

15 ACCU1-LACCU1-H

0 1 0 0 0 0 1 0 0 1 0 0 1 0 0 1 0 1 1 1 0 0 1 1 1 0 1 1 1 0 0 0

031 15

0 1 0 0 0 0 1 0 0 1 0 0 1 0 0 1 1 0 0 0 1 1 0 0 0 1 0 0 0 1 1 1

031

INVD (Ones Complement of ACCU1):

15 ACCU1-LACCU1-H

1 0 1 1 1 1 0 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 1 0 1 1 1 0 0 0031 15

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2 3

Exercise 2.2 : Data Exchange in ACCU1

ACCU1 - L (before)10

CAW

ACCU1 - L (after)0 132

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Exercise 2.3 : Forming Complements

Bit 15 Bit 0

Forming the OnesComplement: INVI

1 . . . . . . . . . . . . 1 0 1

ACCU1-L (before)

Bit 15 Bit 0ACCU1-L (after)

0 . . . . . . . . . . . . 0 1 0