Motorola CPU32 Reference Manual page 105

II
BTST Test a Bit
BTST
Operation:
Assembler
Syntax:
Attributes:
- (bit number) of Destination) :::) Z
BTST On, (ea)
BTST #(data), (ea)
Size
=
(Byte, Long)
Description:
Tests a bit in the destination operand and sets the Z condition code appropriately.
When a data register is the destination, any of the 32 bits can be specified by a modulo 32 bit
number. When a memory location is the destination, the operation 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 instruction.
2. Register - The specified data register contains the bit number.
Condition Codes:
x
N
X Not affected.
N Not affected.
z
v
C
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 12 11 10
9 8
7
6 5 4 3 2
EFFECTIVE ADDRESS
0 0 0 0 1 0 0 0 0 0
I
MODE REGISTER
0 0 0 0 0 0 0 0
BIT NUMBER
o
MOTOROLA
4-52
INSTRUCTION SET CPU32 REFERENCE MANUAL