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Conditional Subtract
SUBC
7-181
Assembly Language Instructions
SUBC affects OV but is not affected by OVM; therefore, the accumulator does
not saturate upon positive or negative overflows when executing this instruc-
tion. The carry bit is affected in the normal manner during this instruction: the
carry bit is cleared (C = 0) if the result of the subtraction generates a borrow
and is set (C = 1) if it does not generate a borrow.
Words 1
Cycles for a Single SUBC Instruction
Program
Operand ROM DARAM SARAM External
DARAM 1 1 1 1+p
SARAM 1 1 1, 2
†
1+p
External 1+d 1+d 1+d 2+d+p
†
If the operand and the code are in the same SARAM block
Cycles for a Repeat (RPT) Execution of an SUBC Instruction
Program
Operand
ROM
DARAM SARAM External
DARAM n n n n+p
SARAM n n n, n+1
†
n+p
External n+nd n+nd n+nd n+1+p+nd
†
If the operand and the code are in the same SARAM block
Example 1 SUBC DAT2 ;(DP = 6)
Before Instruction After Instruction
Data Memory Data Memory
302h 01h 302h 01h
ACC X 04h ACC 0 08h
CC
Example 2 RPT #15
SUBC *
Before Instruction After Instruction
ARP 3 ARP 3
AR3 1000h AR3 1000h
Data Memory Data Memory
1000h 07h 1000h 07h
ACC X 41h ACC 1 20009h
CC
Cycles