Instruction: Subtract two signed values.

SUBS SValue1, < # > SValue2

Result: Difference of signed SValue1 and signed SValue2 is stored in SValue1.

SValue1 (d-field) is the register containing the value to subtract SValue2 from, and is the destination in which to write the result.
SValue2 (s-field) is a register or a 9-bit literal whose value is subtracted from SValue1.

Opcode Table:

–INSTR– ZCRI –CON– –DEST– –SRC–	Z Result	C Result	Result	Clocks
110101 001i 1111 ddddddddd sssssssss	D - S = 0	Signed Overflow	Written	4

Concise Truth Table:

In					Out
Destination	Source	Z	C	Effects	Destination	Z	C
$0000_0001; 1	$0000_0001; 1	-	-	wz wc	$0000_0000; 0	1	0
$0000_0001; 1	$0000_0002; 2	-	-	wz wc	$FFFF_FFFF; -1	0	0
$FFFF_FFFF; -1	$FFFF_FFFF; -1	-	-	wz wc	$0000_0000; 0	1	0
$FFFF_FFFF; -1	$FFFF_FFFE; -2	-	-	wz wc	$0000_0001; 1	0	0
$8000_0001; -2,147,483,647	$0000_0001; 1	-	-	wz wc	$8000_0000; -2,147,483,648	0	0
$8000_0001; -2,147,483,647	$0000_0002; 2	-	-	wz wc	$7FFF_FFFF; 2,147,483,647	0	1
$7FFF_FFFE; 2,147,483,646	$FFFF_FFFF; -1	-	-	wz wc	$7FFF_FFFF; 2,147,483,647	0	0
$7FFF_FFFE; 2,147,483,646	$FFFF_FFFE; -2	-	-	wz wc	$8000_0000; -2,147,483,648	0	1

Explanation

SUBS subtracts the signed SValue2 from the signed SValue1 and stores the result into the SValue1 register.

If the WZ effect is specified, the Z flag is set (1) if SValue1 − SValue2 equals zero. If the WC effect is specified, the C flag is set (1) if the subtraction resulted in a signed overflow. The result is written to SValue1 unless the NR effect is specified.

To subtract signed, multi-long values, use SUB, possibly SUBX, and finally SUBSX. See SUBSX for more information.