Subb – Texas Instruments TMS320C2XX User Manual
Page 331
SUBB
Subtract From Accumulator With Borrow
7-178
Syntax
SUBB
dma
Direct addressing
SUBB
ind [, ARn]
Indirect addressing
Operands
dma:
7 LSBs of the data-memory address
n:
Value from 0 to 7 designating the next auxiliary register
ind:
Select one of the following seven options:
* *+ *– *0+ *0– *BR0+ *BR0–
SUBB
dma
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
1
1
0
0
1
0
0
0
dma
SUBB
ind [, ARn]
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
1
1
0
0
1
0
0
1
ARU
N
NAR
Note:
ARU, N, and NAR are defined in Section 6.3,
Indirect Addressing Mode (page 6-9).
Execution
Increment PC, then ...
(ACC) – (data-memory address) – (logical inversion of C )
→
ACC
Status Bits
Affected by
Affects
OVM
OV and C
This instruction is not affected by SXM.
Description
The content of the addressed data-memory location and the logical inversion
of the carry bit is subtracted from the accumulator with sign extension sup-
pressed. The carry bit is then affected in the normal manner: 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.
The SUBB instruction can be used in performing multiple-precision arithmetic.
Words
1
Cycles for a Single SUBB 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
Opcode
Cycles