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Instruction Set
3-20
RISC 16-Bit CPU
3.4.3 Jumps
Figure 3−11 shows the conditional-jump instruction format.
Figure 3−11. Jump Instruction Format
C 10-Bit PC Offset
15 0
Op-code
8714 13 12 11 10 9 6 5 4 3 2 1
Table 3−13 lists and describes the jump instructions.
Table 3−13.Jump Instructions
Mnemonic S-Reg, D-Reg Operation
JEQ/JZ Label Jump to label if zero bit is set
JNE/JNZ Label Jump to label if zero bit is reset
JC Label Jump to label if carry bit is set
JNC Label Jump to label if carry bit is reset
JN Label Jump to label if negative bit is set
JGE Label Jump to label if (N .XOR. V) = 0
JL Label Jump to label if (N .XOR. V) = 1
JMP
Label Jump to label unconditionally
Conditional jumps support program branching relative to the PC and do not
affect the status bits. The possible jump range is from −511 to +512 words
relative to the PC value at the jump instruction. The 10-bit program-counter
offset is treated as a signed 10-bit value that is doubled and added to the
program counter:
PC
new
= PC
old
+ 2 + PC
offset
× 2