Propeller Manual

ADDABS – Assembly Language Reference
ADDABS
Instruction: Add an absolute value to another value.
ADDABS Value, 〈#〉 SValue
Result: Sum of Value and absolute of signed SValue is stored in Value.
•
Value (d-field) is the register containing the value to add to the absolute of SValue 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 added into Value.
Literal SValues are zero-extended (always positive values) so
ADDABS is best used
with register SValues.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
100010 001i 1111 ddddddddd sssssssss
D + |S| = 0 Unsigned Carry
1
Written 4
1
If S is negative, C Result is the inverse of unsigned borrow (for D - S).
Concise Truth Table:
In Out
Destination
1
Source Z C Effects Destination Z C
$FFFF_FFFD; 4,294,967,293 $0000_0004; 4 - -
wz wc
$0000_0001; 1 0 1
$FFFF_FFFD; 4,294,967,293 $0000_0003; 3 - -
wz wc
$0000_0000; 0 1 1
$FFFF_FFFD; 4,294,967,293 $0000_0002; 2 - -
wz wc
$FFFF_FFFF; 4,294,967,295 0 0
$FFFF_FFFD; 4,294,967,293 $FFFF_FFFF; -1 - -
wz wc
$FFFF_FFFE; 4,294,967,294 0 1
$FFFF_FFFD; 4,294,967,293 $FFFF_FFFE; -2 - -
wz wc
$FFFF_FFFF; 4,294,967,295 0 1
$FFFF_FFFD; 4,294,967,293 $FFFF_FFFD; -3 - -
wz wc
$0000_0000; 0 1 0
$FFFF_FFFD; 4,294,967,293 $FFFF_FFFC; -4 - -
wz wc
$0000_0001; 1 0 0
1
Destination is treated as an unsigned value.
Explanation
ADDABS sums Value and the absolute of SValue together 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 summation resulted in an unsigned carry (32-bit
overflow). The result is written to Value unless the
NR effect is specified.
Page 260 · Propeller Manual v1.1