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; -2,147,483,6481 | 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.
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