Instruction Reference Manual
37
Description
The Interrupt Priority Register, IP is an 8-bit register that forms a stack of the current priority and the other
previous 3 priorities. IPSET 0 forms the lowest priority; IPSET 3 forms the highest priority. These instruc-
tions are privileged. They are implemented for the Rabbit and are not available for the Z180.
•
IPSET 0:
The IPSET 0 instruction shifts the contents of the register holding the previous pri-
orities 2-bits to the left, then sets the Interrupt Priority Register (bits 0 and 1) to 00.
•
IPSET 1:
The IPSET 1 instruction first shifts the contents of the register holding the previous
priorities 2-bits to the left, then sets the Interrupt Priority Register (bits 0 and 1) to 01.
•
IPSET 2:
The IPSET 2 instruction shifts the contents of the register holding the previous pri-
orities 2-bits to the left, then sets the Interrupt Priority Register (bits 0 and 1) to 10.
•
IPSET 3:
The IPSET 3 instruction shifts the contents of the register holding the previous pri-
orities 2-bits to the left, then sets the Interrupt Priority Register (bits 0 and 1) to 11.
IPSET 0
IPSET 1
IPSET 2
IPSET 3
Opcode
Instruction
Clocks
Operation
ED 46
IPSET 0
4 (2,2)
IP = {IP[5:0], 00}
ED 56
IPSET 1
4 (2,2)
IP = {IP[5:0], 01}
ED 4E
IPSET 2
4 (2,2)
IP = {IP[5:0], 10}
ED 5E
IPSET 3
4 (2,2)
IP = {IP[5:0], 11}
Flags
ALTD
I/O
S
Z
L/V
C
F
R
SP
S
D
-
-
-
-
Processor Priority
Effect on Interrupts
0
All interrupts, priority 1,2 and 3 take place after
execution of current non privileged instruction.
1
Only interrupts of priority 2 and 3 take place
after execution of current non privileged
instruction.
2
Only interrupts of priority 3 take place after
execution of current non privileged instruction.
3
All interrupts are suppressed
(except the RST instruction).
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