Rev. 1.50, 10/04, page 328 of 448
10.1.73 SUBC (Subtract with Carry): Arithmetic Instruction
Format
Operation
Instruction Code
Cycle
T Bit
SUBC Rm,Rn
Rn - Rm-T
→
Rn, borrow
→
T
0011nnnnmmmm1010
1 Borrow
Description:
This instruction subtracts the contents of general register Rm and the T bit from the
contents of general register Rn, and stores the result in Rn. A borrow resulting from the operation
is reflected in the T bit. This instruction is used for subtractions exceeding 32 bits.
Notes:
None
Operation:
SUBC(long m, long n) /* SUBC Rm,Rn */
{
unsigned long tmp0,tmp1;
tmp1 = R[n] - R[m];
tmp0 = R[n];
R[n] = tmp1 - T;
if (tmp0<tmp1) T = 1;
else T = 0;
if (tmp1<R[n]) T = 1;
PC += 2;
}
Example:
CLRT
;
R0:R1(64 bits) – R2:R3(64 bits) = R0:R1(64 bits)
SUBC
R3,R1
;
Before execution T = 0, R1 = H'00000000, R3 = H'00000001
;
After execution
T = 1, R1 = H'FFFFFFFF
SUBC
R2,R0
;
Before execution T = 1, R0 = H'00000000, R2 = H'00000000
;
After execution
T = 1, R0 = H'FFFFFFFF
Содержание SuperH SH-4A
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