HT47C20 Holtek Semiconductor Inc, HT47C20 Datasheet - Page 14

• Manufacturer Part Number: HT47C20
• Description: 8-Bit Microcontroller
• Manufacturer: Holtek Semiconductor Inc

Once an interrupt subroutine is serviced, all
other interrupts will be blocked (by clearing the
EMI bit). This scheme may prevent any further
interrupt nesting. Other interrupt requests
may happen during this interval, but only the
interrupt request flag is recorded. If a certain
interrupt needs servicing within the service
routine, the EMI bit and the corresponding bit
of INTC0 or INTC1 may be set allow interrupt
nesting. If the stack is full, the interrupt request
will not be acknowledged, even if the related in-
terrupt is enabled, until the SP is decremented.
If immediate service is desired, the stack must
Register
INTC0
INTC1
(0BH)
(1EH)
Bit No.
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Label
ETBI
ERTI
EMI
TBF
RTF
EEI
EIF
ETI
TF
¾
¾
¾
¾
¾
¾
¾
Control the master (global) interrupt
(1= enabled; 0= disabled)
Control the external interrupt
(1= enabled; 0= disabled)
Control the time base interrupt
(1= enabled; 0= disabled)
Control the real time clock interrupt
(1= enabled; 0= disabled)
External interrupt request flag
(1= active; 0= inactive)
Time base request flag
(1= active; 0= inactive)
Real time clock request flag
(1= active; 0= inactive)
Control the timer/event counter interrupt
(1= enabled; 0=disabled)
Unused bit, read as ²0²
Unused bit, read as ²0²
Unused bit, read as ²0²
Internal timer/event counter request flag
(1= active; 0= inactive)
Unused bit, read as ²0²
Unused bit, read as ²0²
Unused bit, read as ²0²
Unused bit, read as ²0²
INTC register
14
be prevented from becoming full.
All these kinds of interrupt have a wake-up ca-
pability. As an interrupt is serviced, a control
transfer occurs by pushing the program counter
onto the stack and then by branching to subrou-
tines at specified location(s) in the program
memory. Only the program counter is pushed
onto the stack. If the contents of the register
and status register (STATUS) is altered by the
interrupt service program which corrupts the
desired control sequence, the contents must be
saved first.
Function
January 18, 2000
HT47C20