Subtract Reverse Integer With Borrow
SUBRB
13-239
Assembly Language Instructions
Syntax SUBRB
src, dst
Operation
src – dst
– C
dst
Operands
src
general addressing modes (G):
0 0 register (R
n
, 0
n
27)
0 1 direct
1 0 indirect (disp = 0–255, IR0, IR1)
1 1 immediate
dst
register (R
n
, 0
n
27)
Opcode
31 2423 16 87 015
000 11 0
0 10
dst
G
src
Description The difference of the
src, dst
, and C operands is loaded into the
dst
register.
The
dst
and
src
operands are assumed to be signed integers.
Cycles 1
Status Bits These condition flags are modified only if the destination register is R7–R0.
LUF Unaffected
LV 1 if an integer overflow occurs; unchanged otherwise
UF 0
N1 if a negative result is generated; 0 otherwise
Z1 if a 0 result is generated; 0 otherwise
V1 if an integer overflow occurs; 0 otherwise
C1 if a borrow occurs; 0 otherwise
OVM Operation is affected by OVM bit value.
Example SUBRB R4,R6
Before Instruction After Instruction
R4 00 0000 03CB R4 00 0000 03CB
R6 00 0000 0258 R6 00 0000 0172
LUF 0LUF 0
LV 0LV 0
UF 0UF 0
N0N0
Z0Z0
V0V0
C1C0
600 971
370
971
Mode Bit