Rabbit 2000 - Page 84

80 Rabbit 2000/3000 Microprocessor
Description
If the condition f is false, then the instruction is ignored. If the condition f is true, then the instruction loads the
low order byte of the Program Counter, PC, with the data at the memory address in the Stack Pointer, SP, then
loads the high order byte of PC with the data at the memory address immediately following the one held in SP
and the data in SP is then incremented twice.
The condition f is one of the following:
• NZ zero flag not set
• Z zero flag set
• NC carry flag not set
• C carryflagset
• LZ/NV Logic Zero/Overflow flag is not set
• LO/V Logic Zero/Overflow flag is set
• P sign flag not set
• M sign flag set.
RET f
Opcode Instruction Operation
——
C0
C8
D0
D8
E0
E8
F0
F8
RET f
RET NZ
RET Z
RET NC
RET C
RET LZ
RET LO
RET P
RET M
If {f}PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {NZ} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {Z} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {NC} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {C} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {LZ} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {LO} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {P} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
If {M} PC
(low)
= (SP); PC
(high)
= (SP + 1); SP = SP + 2
Clocking: 2; 8 (2,1,2,2,1)
Flags ALTD I/O
S Z L/V C F R SP S D
- - - -