gc80c520a CORERIVER Semiconductor, gc80c520a Datasheet - Page 145

• Manufacturer Part Number: gc80c520a
• Description: Midas1.0 Family Mask Rom/eprom/romless 8-bit Turbo Microcontrollers
• Manufacturer: CORERIVER Semiconductor

RETI
Description:
Operation:
Encoding:
Function:
Example:
MiDAS1.0 Family
Cycles:
Bytes:
Return from interrupt
RETI pops the high-and low-order bytes of the PC successively from the stack,
and restores the interrupt logic to accept additional interrupts at the same
priority level as the one just processed. The Stack Pointer is left decremented
by two. No other registers are affected; the PSW is not automatically restored to
its pre-interrupt status. Program execution continues at the resulting address,
which is generally the instruction immediately after the point at which the
interrupt request was detected. If a lower-or same-level interrupt had been
pending when the RETI instruction is executed, that one instruction will be
executed before the pending interrupt is processed.
The Stack Pointer originally contains the value 0Bh. An interrupt was detected
during the instruction ending at location 0122h. Internal RAM locations 0Ah and
0Bh contain the values 23h and 01h, respectively. The instruction,
RETI
will leave the Stack Pointer equal to 09h and return program execution to
location 0123h.
1
2
RETI
(PC
(SP)
(PC )
(SP)
0
15-8
7-0
←
←
0
)
←
(SP) – 1
(SP) – 1
←
1
((SP))
((SP))
1
0 0 1 0
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