Description:

Subtracts two registers and places the result in the destination register Rd.

Operation:

(i)Rd ← Rd - Rr

Syntax: Operands: Program Counter:

(i)SUB Rd,Rr 0 ≤ d ≤ 31, 0 ≤ r ≤ 31 PC ← PC + 1

16-bit Opcode:

0001

10rd

dddd

rrrr

Status Register and Boolean Formula:

I

T

H

S

V

N

Z

C

-

-

H:

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V:

Set if two's complement overflow resulted from the operation; cleared otherwise.

N:R7

Set if MSB of the result is set; cleared otherwise.

Z:

Set if the result is $00; cleared otherwise.

C:

Set if the absolute value of the contents of Rr is larger than the absolute value of Rd; cleared otherwise.

R (Result) equals Rd after the operation.

Example:

sub r13,r12 ; Subtract r12 from r13
brne noteq ; Branch if r12⇔r13
...
noteq: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1