GMS82524 Datasheet, PDF (52/93 Pages) Hynix Semiconductor – 8-BIT SINGLE-CHIP MICROCONTROLLERS

HYUNDAI MicroElectronics
GMS82512/16/24
14.1 Interrupt Sequence
An interrupt request is held until the interrupt is accepted
or the interrupt latch is cleared to “0” by a reset or an in-
struction. Interrupt acceptance sequence requires 8 f_XIN (2
µs at f_MAIN=4.19MHz) after the completion of the current
instruction execution. The interrupt service task is termi-
nated upon execution of an interrupt return instruction
[RETI].
Interrupt acceptance
1. The interrupt master enable flag (I-flag) is cleared to
“0” to temporarily disable the acceptance of any follow-
ing maskable interrupts. When a non-maskable inter-
rupt is accepted, the acceptance of any following
interrupts is temporarily disabled.
2. Interrupt request flag for the interrupt source accepted is
cleared to “0”.
3. The contents of the program counter (return address)
and the program status word are saved (pushed) onto the
stack area. The stack pointer decreases 3 times.
4. The entry address of the interrupt service program is
read from the vector table address and the entry address
is loaded to the program counter.
5. The instruction stored at the entry address of the inter-
rupt service program is executed.
System clock
Instruction Fetch
Address Bus
PC
SP SP-1
SP-2
V.L. V.H.
New PC
Data Bus
Not used
PCH PCL PSW V.L. ADL ADH
OP code
Internal Read
Internal Write
Interrupt Processing Step
V.L. and V.H. are vector addresses.
ADL and ADH are start addresses of interrupt service routine as vector contents.
Interrupt Service Task
Figure 14-4 Timing chart of Interrupt Acceptance and Interrupt Return Instruction
Basic Interval Timer
Vector Table Address
0FFE6_H
0FFE7_H
012_H
0E3_H
Entry Address
0E312_H
0E_H
0E313_H
2E_H
Correspondence between vector table address for BIT interrupt
and the entry address of the interrupt service program.
A interrupt request is not accepted until the I-flag is set to
“1” even if a requested interrupt has higher priority than
that of the current interrupt being serviced.
When nested interrupt service is required, the I-flag should
be set to “1” by “EI” instruction in the interrupt service
program. In this case, acceptable interrupt sources are se-
lectively enabled by the individual interrupt enable flags.
Saving/Restoring General-purpose Register
During interrupt acceptance processing, the program
counter and the program status word are automatically
saved on the stack, but accumulator and other registers are
not saved itself. These registers are saved by the software
if necessary. Also, when multiple interrupt services are
nested, it is necessary to avoid using the same data memory
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