CONDITIONAL BRANCH INSTRUCTIONS
CJNE
The CJNE instruction compares the first two operands and branches to the specified destination if their values are not equal. If the values are the same, execution continues with the next instruction.
| format | example | Operation | Opcode/ Encoding | Flags affected | Byte | Cycles |
| CJNE @Rn, #immd,offset | CJNE @R1, #24h,label | PC=PC+3 If (Rn) <>#data PC=PC+offset If(Rn) <#data C=1 Else C=0 |
1011011n, #imm 8-bit, offset | C | 3 | 2 |
| CJNE A, #data, offset | CJNE A, #01h, label | PC=PC+3 If A <> #immd PC=PC+offset If A<#immd C=1 Else C=0 |
10110100, #immd, offset | C | 3 | 2 |
| CJNE A, direct, offset | CJNE A, 60h, label | PC=PC+3 If A<> (direct) PC=PC+offset If A < (direct) C=1 Else C=0 |
10110101, direct 8-bit adder, offset | C | 3 | 2 |
| CJNE Rn, #immd, offset | CJNE R6, #12h, label | PC=PC+3 If Rn <> immediate PC=PC + offset If Rn < immd C=1 Else C=0 |
10111nnn, #immd 8-bit, offset | C | 3 | 2 |
DJNZ
The DJNZ instruction decrements the byte indicated by the first operand and, if the resulting value is not zero, branches to the address specified in the second operand.
| format | example | Operation | Opcode/ Encoding | Flags affected | Byte | Cycles |
| DJNZ direct, offset | DJNZ 40h,label | PC PC+2 (direct)=(direct)-1 If (direct)<>0 PC=PC+offset |
11010101, direct addr 8-bit, offset 8-bit | none | 3 | 2 |
| DJNZ Rn, offset | DJNZ R6, Label | PC=PC+2 Rn=Rn-1 If Rn<>0 PC=PC+offset |
11011nnn, offset 8-bit | none | 2 | 2 |
JB
The JB instruction branches to the address specified in the second operand if the value of the bit specified in the first operand is 1. The bit that is tested is not modified. No flags are affected by this instruction.
| format | example | Operation | Opcode/Encoding | Flags affected | Byte | Cycles |
| JB bit, offset | JB P1.2, label | PC=PC+3 If (bit)=1 PC=PC+offset |
00100000, bit, offset | none | 3 | 2 |
JNB
The JNB instruction branches to the specified address if the specified bit operand has a value of 0. Otherwise, execution continues with the next instruction. No flags are affected by this instruction.
| format | example | Operation | Opcode/Encoding | Flags affected | Byte | Cycles |
| JNB bit, offset | JNB P1.3, label | PC=PC+3 If (bit)=0 PC=PC+offset |
00100000, bit, offset | none | 3 | 2 |
JBC
The JBC Jump to branch address if Bit set, clear bit after branch
JBC bit, offset
PC=PC+3
If bit set
then
Jump to specified address if bit is set
clear the bit after
else
continue normal execution
Note
When this instruction is used to modify an output port, the value used as the port data is read from the output data latch, not the input pins of the port.
| format | example | Operation | Opcode/Encoding | Flags affected | Byte | Cycles |
| JBC bit, offset | JBC P1.2, 44h | PC=PC+3 If (bit)=1 (bit)=0 PC=PC+offset |
00010000, bit, offset | none | 3 | 2 |
JC
Jump if carry bit in PSW is set
If not set; execution continues with the next instruction.
No flags are affected by this instruction.
| format | example | Operation | Opcode/Encoding | Flags affected | Byte | Cycles |
| JC offset | JC label | PC=PC+2 If C=1 PC=PC+offset |
01000000, offset | none | 2 | 2 |
JNC
Jump if carry not set (i.e. carry clear)
Otherwise, execution continues with the next instruction.
No flags are affected by this instruction.
| format | example | Operation | Opcode/Encoding | Flags affected | Byte | Cycles |
| JNC offset | JC label | PC=PC+2 If C=0 PC=PC+offset |
01010000, offset | none | 2 | 2 |
JZ
Jump if result in Accumulator is zero
Otherwise, the next instruction is executed.
Neither the accumulator nor any flags are modified by this instruction.
| format | example | Operation | Opcode/Encoding | Flags affected | Byte | Cycles |
| JZ offset | JZ label | PC=PC+2 If A=0 PC=PC+offset |
01100000, offset | none | 2 | 2 |
JNZ
The JNZ instruction transfers control to the specified address if the value in the accumulator is not 0. If the accumulator has a value of 0, the next instruction is executed. Neither the accumulator nor any flags are modified by this instruction.
| format | example | Operation | Opcode/ Encoding | Flags affected | Byte | Cycles |
| JNZ offset | JNZ label | PC=PC+2 If A< >0 PC=PC+offset |
01110000, offset | none | 2 | 2 |