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7 DETAILS OF INSTRUCTIONS
7-106
EPSON
S1C17 FAMILY S1C17 CORE MANUAL
sbc
%rd, %rs
sbc/c %rd, %rs
sbc/nc %rd, %rs
Function
16-bit subtraction with borrow
Standard)
rd
(15:0)
← rd(15:0) - rs(15:0) - C, rd(23:16) ← 0
Extension 1) rd(15:0)
← rs(15:0) - imm13(zero extended) - C, rd(23:16) ← 0
Extension 2) rd(15:0)
← rs(15:0) - imm16 - C, rd(23:16) ← 0
Code
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
0 0 1 1 1 0
r d
1 0 1 1
r s
sbc
|
0 0 1 1 1 0
r d
0 0 1 1
r s
sbc/c
|
0 0 1 1 1 0
r d
0 1 1 1
r s
sbc/nc
|
Flag
IL IE
C
V
Z
N
– –
sbc
|
– – –
sbc/c, sbc/nc
|
Mode
Src:Register direct %rs = %r0 to %r7
Dst:Register direct %rd = %r0 to %r7
CLK
One cycle
Description (1) Standard
sbc
%rd,%rs
; rd
← rd - rs - C
The content of the rs register and C (carry) flag are subtracted from the rd register. The
operation is performed in 16-bit size, and bits 23–16 of the rd register are set to 0.
(2) Extension 1
ext
imm13
sbc
%rd,%rs
; rd
← rs - imm13 - C
The 13-bit immediate imm13 and C (carry) flag are subtracted from the rs register after being
zero-extended, and the result is loaded into the rd register. The operation is performed in 16-bit
size, and bits 23–16 of the rd register are set to 0. The content of the rs register is not altered.
(3) Extension 2
ext
imm13
; imm13(2:0) = imm16(15:13)
ext
imm13
; = imm16(12:0)
sbc
%rd,%rs
; rd
← rs - imm16 - C
The 16-bit immediate imm16 and C (carry) flag are subtracted from the rs register, and the
result is loaded into the rd register. The operation is performed in 16-bit size, and bits 23–16 of
the rd register are set to 0. The content of the rs register is not altered.
(4) Conditional execution
The /c or /nc suffix on the opcode specifies conditional execution.
sbc/c
Executed as sbc when the C flag is 1 or executed as nop when the flag is 0
sbc/nc Executed as sbc when the C flag is 0 or executed as nop when the flag is 1
In this case, the ext instruction can be used to extend the operand.
(5) Delayed slot instruction
This instruction may be executed as a delayed slot instruction by writing it directly after
a branch instruction with the “d” bit. In this case, extension of the immediate by the ext
instruction cannot be performed.
Example
(1) sbc
%r0,%r1
; r0 = r0 - r1 - C
(2) Subtraction of 32-bit data
data 1 = {r2, r1}, data2 = {r4, r3}, result = {r2, r1}
sub
%r1,%r3
; Subtraction of the low-order word
sbc
%r2,%r4
; Subtraction of the high-order word