TJNZ
Instruction: Test value and jump to address if not zero.
TJNZ Value, < # >Address
- Value (d-field) is the register to test.
- Address (s-field) is the register or a 9-bit literal whose value is the address to jump to when Value contains a non-zero number.
Opcode Table:
–INSTR– ZCRI –CON– –DEST– –SRC– | Z Result | C Result | Result | Clocks |
111010 000i 1111 ddddddddd sssssssss | D = 0 | 0 | Not Written | 4 or 8 |
Concise Truth Table:
In | Out | ||||||
Destination | Source | Z | C | Effects | Destination1 | Z | C |
$0000_0000; 0 | $----_----; - | - | - | wr wz wc | $0000_0000; 0 | 1 | 0 |
$0000_0001; 1 | $----_----; - | - | - | wr wz wc | $0000_0001; 1 | 0 | 0 |
1 Destination is not written unless the WR effect is given.
Explanation
TJNZ tests the Value register and jumps to Address if it contains a non-zero number.
When the WZ effect is specified, the Z flag is set (1) if the Value register contains zero.
TJNZ requires a different amount of clock cycles depending on whether or not it has to jump. If it must jump it takes 4 clock cycles, if no jump occurs it takes 8 clock cycles. Since loops utilizing TJNZ need to be fast, it is optimized in this way for speed.
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