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lAS
Test and Set an Operand
lAS
Operation:
Destination Tested => Condition Codes; 1 => bit 7 of Destination
Assembler
Syntax:
Attributes:
TAS (ea)
Size
=
(Byte)
Description:
Tests and sets the byte operand addressed by the effective address field.
The
instruction tests the current value of the operand and sets the Nand
Z condition bits
appropriately. TAS also sets the high-order bit of the operand. The operation uses a read-modify-
write memory cycle that completes the operation without interruption. This instruction supports
use of a flag to coordinate several processors.
Condition Codes:
x
N
z
v
C
o
0
X
Not affected.
N Set if the most significant bit of the operand is currently set.
Z Set if the operand was zero. Cleared otherwise.
V
Always cleared.
C Always cleared.
Instruction Format:
15
14
13
12
11
10
9
8
7
6
0
1
0
0
1
0
1
0
1
1
CPU32 REFERENCE MANUAL
INSTRUCTION SET
Cleared otherwise.
5
4
3
2
o
EFFECTIVE ADDRESS
MODE
I
REGISTER
MOTOROLA
4-167
III
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