Propeller Manual

ABSNEG – Assembly Language Reference
ABSNEG
Instruction: Get the negative of a number’s absolute value.
ABSNEG NValue, 〈#〉 SValue
Result: Absolute negative of SValue is stored in NValue.
•
NValue (d-field) is the register in which to write the negative of SValue’s absolute
value.
•
SValue (s-field) is a register or a 9-bit literal whose absolute negative value will be
written to NValue.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
101011 001i 1111 ddddddddd sssssssss
Result = 0 S[31] Written 4
Concise Truth Table:
In Out
Destination Source Z C Effects Destination Z C
$----_----; - $0000_0001; 1 - -
wz wc
$FFFF_FFFF; -1 0 0
$----_----; - $0000_0000; 0 - -
wz wc
$0000_0000; 0 1 0
$----_----; - $FFFF_FFFF; -1 - -
wz wc
$FFFF_FFFF; -1 0 1
$----_----; - $7FFF_FFFF; 2,147,483,647 - -
wz wc
$8000_0001; -2,147,483,647 0 0
$----_----; - $8000_0000; -2,147,483,648 - -
wz wc
$8000_0000; -2,147,483,648 0 1
$----_----; - $8000_0001; -2,147,483,647 - -
wz wc
$8000_0001; -2,147,483,647 0 1
Explanation
ABSNEG negates the absolute value of SValue and writes the result into NValue.
If the
WZ effect is specified, the Z flag is set (1) if SValue is zero. If the WC effect is specified,
the C flag is set (1) if SValue is negative, or cleared (0) if SValue is positive. The result is
written to NValue unless the
NR effect is specified.
Literal SValues are zero-extended, so
ABS is really best used with register SValues.
Page 258 · Propeller Manual v1.1