Maxim Integrated DS4830 Optical Microcontroller - Manual (Page 215)

DS4830 User’s Guide
215
SR Shift Accumulator Right
SRA / SRA2 / SRA4 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
msb while the SRA, SRA2, and SRA4 instructions effectively shift a copy of the current msb into
the accumulator, thereby preserving any sign orientation. For each shift iteration, the
accumulator lsb 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
0
Acc.15  0; Acc.[14:0] Acc.[15:1]; C  Acc.0
Encoding:
15 0
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:
15 0
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