Z8
®
CPU
User Manual
UM001604-0108
Instruction Description
181
Enable Interrupts
Syntax
EI
Instruction Format
Operation
IMR (7)
←
0
Bit 7 of Control Register
FBh
(the Interrupt Mask Register) is set to 1. This allows poten-
tially enabled interrupts to become enabled.
Example
If Control Register
FBh
contains
0Ah
(
00001010
) (interrupts IRQ1 and IRQ3 are
selected), the statement:
EI
Op Code: 9F
sets Control Register
FBh
to
8Ah
(
10001010b
) and enables IRQ1 and IRQ3.
Cycles
OPC
(Hex)
OPC
6
9F
Flag
Description
C
Unaffected
Z
Unaffected
S
Unaffected
V
Unaffected
D
Unaffected
H
Unaffected