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TSTA
Operation:
(A) – $00
Description:
Subtracts $00 from the content of accumulator A and sets the condition
codes accordingly.
The subtraction is accomplished internally without modifying A.
The TSTA instruction provides limited information when testing un-
signed values. Since no unsigned value is less than zero, BLO and BLS
have no utility following TSTA. While BHI can be used after TST, it per-
forms the same function as BNE, which is preferred. After testing signed
values, all signed branches are available.
Condition Codes and Boolean Formulas:
S
–
N:
Z:
V:
C:
Addressing Modes, Machine Code, and Execution Times:
Source Form
TSTA
CPU12
REFERENCE MANUAL
Test A
X
H
I
N
Z
∆
∆
–
–
–
Set if MSB of result is set; cleared otherwise.
Set if result is $00; cleared otherwise.
0; Cleared.
0; Cleared.
Address Mode
INH
INSTRUCTION GLOSSARY
V
C
0
0
Object Code
97
TSTA
Cycles
Access Detail
1
O
MOTOROLA
6-207
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