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S1C17 CORE MANUAL
Seiko Epson Corporation
7-131
(Rev. 1.2)
sub.a %sp, imm7
Function
24-bit subtraction
Standard)
sp(23:0)
←
sp(23:0) -
imm7
(zero extended)
Extension 1) sp(23:0)
←
sp(23:0) -
imm20
(zero extended)
Extension 2) sp(23:0)
←
sp(23:0) -
imm24
Code
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 1 1 0 1 1 0 0 0
imm7
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Flag
IL IE C V Z N
– – – – – –
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Mode
Src: Immediate data (unsigned)
Dst: Register direct
%sp
CLK
One cycle
Description
(1) Standard
sub.a %sp,imm7
; sp
←
sp - imm7
The 7-bit immediate
imm7
is subtracted from the stack pointer SP after being zero-extended.
(2) Extension 1
ext imm13
; = imm20(19:7)
sub.a %sp,imm7
; sp
←
sp - imm20, imm7 = imm20(6:0)
The 20-bit immediate
imm20
is subtracted from the stack pointer SP after being zero-extended.
(3) Extension 2
ext imm4
;
imm4(3:0) = imm24(23:20)
ext imm13
; = imm24(19:7)
sub.a %sp,imm7
; sp
←
sp - imm24, imm7 = imm24(6:0)
The 24-bit immediate
imm24
is subtracted from the stack pointer SP.
(4) 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.a %sp,0x7c
; sp = sp - 0x7c
(2)
ext 0x1fff
sub.a %sp,0x7c
; sp = sp - 0xffffc
Caution
The 2 low-order bits of the subtruction results are always loaded to the SP as 0.