Maxim-integrated MAXQ622 Manual do Utilizador descarregar pdf (Página 233)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 16-23

SRA/SRA2/SRA4

Shift Accumulator Right

Shift Accumulator Right Arithmetically One, Two, or Four Times

Description:

Shifts the active accumulator right once for the SR, SRA instructions and 2 or 4 times respectively

for the SRA2, SRA4 instructions. The SR instruction shifts a 0 into the accumulator msbit while the

SRA, SRA2, and SRA4 instructions effectively shift a copy of the current msbit into the accumulator,

thereby preserving any sign orientation. For each shift iteration, the accumulator lsbit is shifted into

the Carry (C) flag.

Status Flags:

C, S (changes for SR only), Z

SR Operation:

15 Active Accumulator (Acc) 0 Carry Flag

→ → →

Acc.15 ← 0; Acc.[14:0] ← Acc.[15:1]; C ← Acc.0

Encoding:

1000 1010 1010 1010

Example(s):

; Acc = A345h, C=1, S=1, Z=0

SR ; Acc = 51A2h, C=1, S=0, Z=0

SR ; Acc = 28D1h, C=0, S=0, Z=0

SRA Operation:

15 Active Accumulator (Acc) 0 Carry Flag

→ → →

Acc.[14:0] ← Acc.[15:1]

Acc.15 ← Acc.15

C ← Acc.0

Encoding:

1000 1010 1111 1010

Example(s):

; Acc = 0003h, C=0, Z=0

SRA ; Acc = 0001h, C=1, Z=0

SRA ; Acc = 0000h, C=1, Z=1

SRA2 Operation:

15 Active Accumulator (Acc) 0 Carry Flag

→ → →

Acc.[13:0] ← Acc.[15:2]

Acc.[15:14] ← Acc.15

C ← Acc.1

Encoding:

1000 1010 1110 1010

Example(s):

; Acc = 0003h, C=0, Z=0

SRA2 ; Acc = 0000h, C=1, Z=1

1 2 ... 228 229 230 231 232 233 234 235 236 237 238 ... 254 255

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