M166 Datasheet, PDF (38/127 Pages) Siemens Semiconductor Group – C16x Family of Siemens 16-Bit CMOS Single-Chip Microcontrollers

30Mar98@15:00h
C166 Family Instruction Set
Instruction Description
ASHR
Arithmetic Shift Right
ASHR
Syntax
Operation
Data Types
Description
ASHR op1, op2
(count) ← (op2)
(V) ← 0
(C) ← 0
DO WHILE (count) ≠ 0
(V) ← (C) ∨ (V)
(C) ← (op1₀)
(op1_n) ← (op1_n+1) [n=0...14]
(count) ← (count) - 1
END WHILE
WORD
Arithmetically shifts the destination word operand op1 right by as many
times as specified in the source operand op2. To preserve the sign of the
original operand op1, the most significant bits of the result are filled with
zeros if the original MSB was a 0 or with ones if the original MSB was a 1.
The Overflow flag is used as a Rounding flag. The LSB is shifted into the
Carry. Only shift values between 0 and 15 are allowed. When using a
GPR as the count control, only the least significant 4 bits are used.
Condition Flags
E
Z
V
C
N
0
*
S
S
*
Addressing Modes
E Always cleared.
Z Set if result equals zero. Cleared otherwise.
V Set if in any cycle of the shift operation a 1 is shifted out of the carry
flag. Cleared for a shift count of zero.
C The carry flag is set according to the last LSB shifted out of op1.
Cleared for a shift count of zero.
N Set if the most significant bit of the result is set. Cleared otherwise.
Mnemonic
ASHR
ASHR
Rw_n, Rw_m
Rw_n, #data4
Format
AC nm
BC #n
Bytes
2
2
Semiconductor Group
38
Version 1.2, 12.97