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TAS
Operation:
Assembler
Syntax:
Attributes:
Description:
field. The instruction tests the current value of the operand and sets the N and Z con-
dition bits appropriately. TAS also sets the high-order bit of the operand. The opera-
tion 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
—
*
*
X
Not affected.
N
Set if the most significant bit of the operand is currently set. Cleared otherwise.
Z
Set if the operand was zero. Cleared otherwise.
V
Always cleared.
C
Always cleared.
Instruction Format:
15
14
13
0
1
0
MOTOROLA
4-162
Test and Set an Operand
Destination Tested → Condition Codes; 1 → bit 7 of Destination
TAS 〈ea〉
Size = (Byte)
Tests and sets the byte operand addressed by the effective address
V
C
0
0
12
11
10
9
0
1
0
1
INSTRUCTION SET
8
7
6
5
0
1
1
TAS
4
3
2
1
EFFECTIVE ADDRESS
MODE
REGISTER
REFERENCE MANUAL
0
CPU32
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