Zilog Z08470 - Manual (Page 193)

UM008007-0715 Z80 Instruction Description
Z80 CPU
User Manual
181
EI
Operation
IFF ← 1
Op Code
EI
Operands
None.
Description
The enable interrupt instruction sets both interrupt enable flip flops (IFFI and IFF2) to a
logic 1, allowing recognition of any maskable interrupt.
During the execution of this instruction and the following instruction, maskable interrupts
are disabled.
Condition Bits Affected
None.
Example
When the CPU executes an EI RETI instruction, the maskable interrupt is enabled then
upon the execution of an the RETI instruction.
M Cycles T States 4 MHz E.T.
1 4 1.00
1 1 1 1 1 0 1 1 FB
Note: