HT82K68 Holtek Semiconductor Inc, HT82K68 Datasheet - Page 12

• Manufacturer Part Number: HT82K68
• Description: Multimedia Keyboard Encoder OTP
• Manufacturer: Holtek Semiconductor Inc

will be serviced on the latter of the two T2
pulses, if the corresponding interrupts are en-
abled. In the case of simultaneous requests, the
following table shows the priority that is ap-
plied. These can be masked by resetting the
EMI bit.
The timer counter interrupt request flag (T0F),
enable timer counter bit (ET0I), and enable
master interrupt bit (EMI) constitute an inter-
rupt control register (INTC) which is located at
0BH in the data memory. EMI, ET0I, are used
to control the enabling/disabling of interrupts.
These bits prevent the requested interrupt
from being serviced. Once the interrupt request
flags (T0F) are set, they will remain in the
INTC register until the interrupts are serviced
or cleared by a software instruction.
It is suggested that a program does not use the
²CALL subroutine² within the interrupt sub-
routine. Because interrupts often occur in an un-
predictable manner or need to be serviced
immediately in some applications, if only one
stack is left and enabling the interrupt is not well
No.
Register
a
(0BH)
INTC
Timer counter overflow
Interrupt Source
Bit No.
0
1
2
3
4
5
6
7
Label
ET0I
EMI
T0F
¾
¾
¾
¾
¾
Controls the master (global) interrupt
(1= enabled; 0= disabled)
Undefined, read as "0"; programming must be "0"
Controls the timer counter interrupt
(1= enabled; 0= disabled)
Undefined, read as "0"
Undefined, read as "0"; programming must be "0"
Internal timer counter request flag
(1= active; 0= inactive)
Undefined, read as "0"
Unused bit, read as "0"
Vector
Preliminary
08H
INTC register
12
controlled, once the ²CALL subroutine² operates in
the interrupt subroutine it will damage the original
control sequence.
Oscillator configuration
There are two oscillator circuits in HT82K68E.
Both are designed for system clocks; the RC os-
cillator and the Crystal oscillator, which are de-
termined by mask options. No matter what
oscillator type is selected, the signal provides
the system clock. The HALT mode stops the
system oscillator and resists the external signal
to conserve power.
Crystal Oscillator
OSC1
OSC2
Function
System oscillator
(NMOS Open
Drain Output)
f
SYS
/4
V
DD
HT82K68E
August 8, 2000
OSC1
OSC2
RC Oscillator