7 DETAILS OF INSTRUCTIONS
S1C17 FAMILY S1C17 CORE MANUAL
EPSON
7-113
sub
%rd, %rs
sub/c %rd, %rs
sub/nc %rd, %rs
Function
16-bit subtraction
Standard)
rd
(15:0)
← rd(15:0) - rs(15:0), rd(23:16) ← 0
Extension 1) rd(15:0)
← rs(15:0) - imm13(zero extended), rd(23:16) ← 0
Extension 2) rd(15:0)
← rs(15:0) - imm16, 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 0
r s
sub
|
0 0 1 1 1 0
r d
0 0 1 0
r s
sub/c
|
0 0 1 1 1 0
r d
0 1 1 0
r s
sub/nc
|
Flag
IL IE
C
V
Z
N
– –
sub
|
– – –
sub/c, sub/nc
|
Mode
Src:Register direct %rs = %r0 to %r7
Dst:Register direct %rd = %r0 to %r7
CLK
One cycle
Description (1) Standard
sub
%rd,%rs
; rd
← rd - rs
The content of the rs register is 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
sub
%rd,%rs
; rd
← rs - imm13
The 13-bit immediate imm13 is 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)
sub
%rd,%rs
; rd
← rs - imm16
The 16-bit immediate imm16 is 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.
sub/c
Executed as sub when the C flag is 1 or executed as nop when the flag is 0
sub/nc Executed as sub 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) sub
%r0,%r0
; r0 = r0 - r0
(2) ext
0x1
ext
0x1fff
sub
%r1,%r2
; r1 = r2 - 0x3fff