Instruction: Subtract an absolute value from another value.

SUBABS Value, < # > SValue

Result: Difference of Value and absolute of signed SValue is stored in Value.

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

Opcode Table:

–INSTR– ZCRI –CON– –DEST– –SRC–	Z Result	C Result	Result	Clocks
100011 001i 1111 ddddddddd sssssssss	D - \|S\| = 0	Unsigned Borrow¹	Written	4

¹ If S is negative, C Result is the inverse of unsigned carry (for D + S).

Concise Truth Table:

In					Out
Destination¹	Source	Z	C	Effects	Destination	Z	C
$0000_0003; 3	$FFFF_FFFC; -4	-	-	wz wc	$FFFF_FFFF; 4,294,967,295	0	0
$0000_0003; 3	$FFFF_FFFD; -3	-	-	wz wc	$0000_0000; 0	1	1
$0000_0003; 3	$FFFF_FFFE; -2	-	-	wz wc	$0000_0001; 1	0	1
$0000_0003; 3	$FFFF_FFFF; -1	-	-	wz wc	$0000_0002; 2	0	1
$0000_0003; 3	$0000_0002; 2	-	-	wz wc	$0000_0001; 1	0	0
$0000_0003; 3	$0000_0003; 3	-	-	wz wc	$0000_0000; 0	1	0
$0000_0003; 3	$0000_0004; 4	-	-	wz wc	$FFFF_FFFF; 4,294,967,295	0	1

¹ Destination is treated as an unsigned value.

Explanation

SUBABS subtracts the absolute of SValue from Value and stores the result into the Value register.

If the WZ effect is specified, the Z flag is set (1) if Value − |SValue| equals zero. If the WC effect is specified, the C flag is set (1) if the subtraction resulted in an unsigned borrow (32 bit overflow). The result is written to Value unless the NR effect is specified.