Propeller Manual

NEGC – Assembly Language Reference
NEGC
Instruction: Get a value, or its additive inverse, based on C.
NEGC RValue, 〈#〉 Value
Result: Value or –Value is stored in RValue.
•
RValue (d-field) is the register in which to write Value or –Value.
•
Value (s-field) is a register or a 9-bit literal whose value (if C = 0) or additive inverse
value (if C = 1) will be written to RValue.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– Z Result C Result Result Clocks
101100 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 - 0
wz wc
$FFFF_FFFF; -1 0 1
$----_----; - $FFFF_FFFF; -1 - 1
wz wc
$0000_0001; 1 0 1
$----_----; - $0000_0000; 0 - x
wz wc
$0000_0000; 0 1 0
$----_----; - $0000_0001; 1 - 0
wz wc
$0000_0001; 1 0 0
$----_----; - $0000_0001; 1 - 1
wz wc
$FFFF_FFFF; -1 0 0
$----_----; - $7FFF_FFFF; 2,147,483,647 - 0
wz wc
$7FFF_FFFF; 2,147,483,647 0 0
$----_----; - $7FFF_FFFF; 2,147,483,647 - 1
wz wc
$8000_0001; -2,147,483,647 0 0
$----_----; - $8000_0000; -2,147,483,648 - x
wz wc
$8000_0000; -2,147,483,648
1
0 1
$----_----; - $8000_0001; -2,147,483,647 - 0
wz wc
$8000_0001; -2,147,483,647 0 1
$----_----; - $8000_0001; -2,147,483,647 - 1
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
NEGC stores Value (if C = 0) or –Value (if C = 1) into RValue.
If the
WZ effect is specified, the Z flag is set (1) if Value is zero. If the WC effect is specified,
the C flag is set (1) if Value is negative or cleared (0) if Value is positive. The result is
written to RValue unless the
NR effect is specified.
Page 320 · Propeller Manual v1.1