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BTST
Operation:
Assembler
Syntax:
Attributes:
Description:
appropriately. When a data register is the destination, any of the 32 bits can be spec-
ified by a modulo 32 bit number. When a memory location is the destination, the oper-
ation is a byte operation, and the bit number is modulo 8. In all cases, bit zero refers
to the least significant bit. The bit number for this operation can be specified in either
of two ways:
1. Immediate — The bit number is specified by a second word of the instruc-
tion.
2. Register — The specified data register contains the bit number.
Condition Codes:
X
N
Z
—
—
*
X
Not affected.
N
Not affected.
Z
Set if the bit tested is zero. Cleared otherwise.
V
Not affected.
C
Not affected.
Instruction Format (Bit Number Static, specified as immediate data):
15
14
13
0
0
0
0
0
0
CPU32
REFERENCE MANUAL
Test a Bit
– (〈bit number〉 of Destination) → Z
BTST Dn, 〈ea〉
BTST #〈data〉, 〈ea〉
Size = (Byte, Long)
Tests a bit in the destination operand and sets the Z condition code
V
C
—
—
12
11
10
9
0
1
0
0
0
0
0
0
INSTRUCTION SET
8
7
6
5
0
0
0
0
BTST
4
3
2
1
EFFECTIVE ADDRESS
MODE
REGISTER
BIT NUMBER
MOTOROLA
0
4-47
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