GMS81508B HYNIX [Hynix Semiconductor], GMS81508B Datasheet - Page 62

• Manufacturer Part Number: GMS81508B
• Description: HYUNDAI MICRO ELECTRONICS 8-BIT SINGLE-CHIP MICROCONTROLLERS
• Manufacturer: HYNIX [Hynix Semiconductor]

HYUNDAI MicroElectronics
16.1 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
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
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.
DEC. 1999 Ver 1.04
Correspondence between vector table address for BIT interrupt
and the entry address of the interrupt service program.
s at f
0FFE6
0FFE7
“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.
MAIN
Basic Interval Timer
Vector Table Address
H
H
System clock
Instruction Fetch
Address Bus
Data Bus
Internal Read
Internal Write
V.L. and V.H. are vector addresses.
ADL and ADH are start addresses of interrupt service routine as vector contents.
=4.19MHz) after the completion of the current
012
0E3
H
H
Figure 16-4 Timing chart of Interrupt Acceptance and Interrupt Return Instruction
0E312
0E313
Not used
PC
H
H
Entry Address
0E
2E
SP
Interrupt Processing Step
H
H
PCH
f
XIN
SP-1
(2
PCL
PSW
SP-2
2. Interrupt request flag for the interrupt source accepted is
3. The contents of the program counter (return address)
4. The entry address of the interrupt service program is
5. The instruction stored at the entry address of the inter-
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
cleared to “0”.
and the program status word are saved (pushed) onto the
stack area. The stack pointer decreases 3 times.
read from the vector table address and the entry address
is loaded to the program counter.
rupt service program is executed.
V.L.
V.L.
ADL
V.H.
ADH
Interrupt Service Task
GMS81508B/16B/24B
New PC
OP code
59