Propeller Manual

3: Assembly Language Reference – NEG
NEG
Instruction: Get the negative of a number.
NEG NValue, 〈#〉 SValue
Result: –SValue is stored in NValue.
•
NValue (d-field) is the register in which to write the negative of SValue.
•
SValue (s-field) is a register or a 9-bit literal whose negative value will be written to
NValue.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
101001 001i 1111 ddddddddd sssssssss
Result = 0 S[31] Written 4
Concise Truth Table:
In Out
Destination Source Z C Effects Destination Z C
$----_----; - $FFFF_FFFF; -1 - -
wz wc
$0000_0001; 1 0 1
$----_----; - $0000_0000; 0 - -
wz wc
$0000_0000; 0 1 0
$----_----; - $0000_0001; 1 - -
wz wc
$FFFF_FFFF; -1 0 0
$----_----; - $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
1
0 1
$----_----; - $8000_0001; -2,147,483,647 - -
wz wc
$7FFF_FFFF; 2,147,483,647 0 1
1
The smallest negative number (-2,147,483,648) has no corresponding positive value in 32-bit two’s-complement math.
Explanation
NEG stores negative SValue 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.
Propeller Manual v1.1 · Page 319