HMS87C1304A Datasheet, PDF (51/70 Pages) Hynix Semiconductor – CMOS SINGLE-CHIP 8-BIT MICROCONTROLLER

HYUNDAI MicroElectronics
HMS87C1304A/HMS87C1302A
[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
ry _{Data Bus}
Not used
PCH PCL PSW V.L. ADL ADH
OP code
a _{Internal Read}
in _{Internal Write}
lim ^{Interrupt Processing Step}
V.L. and V.H. are vector addresses.
e ADL and ADH are start addresses of interrupt service routine as vector contents.
Interrupt Service Task
Pr ^{Figure 15-3 Timing chart of Interrupt Acceptance and Interrupt Return Instruction}
Basic Interval Timer
Vector Table Address
Entry Address
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.
0FFE6_H
0FFE7_H
012_H
0E3_H
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
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
area for saving registers.
The following method is used to save/restore the general-
purpose registers.
Jan. 2001
Preliminary
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