Zilog Z80380 - Manual (Page 83)

5-49
Z380 ™
U SER ' S M ANUAL Z ILOG
DC-8297-03
EI
ENABLE INTERRUPTS
EI [n]
Operation: if (n is present) then begin
for i=1 to 4 begin
if (n(i) = 1) then begin
IER(i-1)
←
1
end
end
if (n(0) = 1) then begin
SR(5)
←
1
end
end
else begin
SR(5)
←
1
end
If an argument is present, enable the selected interrupts by setting the appropriate enable
bits in the Interrupt Enable Register, and then set the Interrupt Enable Flag (IEF1) in the
Select Register (SR) if the least-significant bit of the argument is set, enabling maskable
interrupts. Bits 7-5 of the argument are ignored.
If no argument is present, IEF1 in the SR is set to 1, enabling maskable interrupts.
Note that during the execution of this instruction and the following instruction, maskable
interrupts are not sampled.
Flags: S: Unaffected
Z: Unaffected
H: Unaffected
V: Unaffected
N: Unaffected
C: Unaffected
Addressing Execute
Mode Syntax Instruction Format Time Note
EI 11111011 2
EI n 11011101 11111011 —n—— 2