HT45R38
Bit No.
Label
EMI
Function
Controls the master (global) interrupt (1= enabled; 0= disabled)
Controls the external interrupt 0 (1= enabled; 0= disabled)
Controls the external interrupt 1 (1= enabled; 0= disabled)
Controls the Timer/Event Counter 0 interrupt (1= enabled; 0= disabled)
External interrupt 0 request flag (1= active; 0= inactive)
External interrupt 1 request flag (1= active; 0= inactive)
Internal Timer/Event Counter 0 request flag (1= active; 0= inactive)
Unused bit, read as ²0²
0
1
2
3
4
5
6
7
EEI0
EEI1
ET0I
EIF0
EIF1
T0F
¾
INTC0 (0BH) Register
Bit No.
Label
Function
0
1
ERCOCI Controls the external RC oscillation converter interrupt (1= enabled; 0= disabled)
ET1I
EADI
¾
Controls the Timer/Event Counter 1 interrupt (1= enabled; 0= disabled)
Control the A/D converter interrupt (1= enabled; 0= disabled)
Unused bit, read as ²0²
2
3, 7
4
RCOCF External RC oscillation converter request flag (1= active; 0= inactive)
5
T1F
Internal Timer/Event Counter 1 request flag (1= active; 0= inactive)
A/D converter request flag (1= active; 0= inactive)
6
ADF
INTC1 (1EH) Register
The Timer/Event Counter 0 interrupt request flag, T0F,
external interrupt 1 request flag, EIF1, external interrupt
0 request flag, EIF0, enable Timer/Event Counter 0 in-
terrupt bit, ET0I, enable external interrupt 1 bit, EEI1,
enable external interrupt 0 bit, EEI0, and enable master
interrupt bit, EMI, form the interrupt control register 0,
INTC0, which is located at ²0BH² in the RAM.
Oscillator Configuration
There are two oscillator circuits in the microcontroller.
V
D
D
O
S
C
1
O
S
C
1
4
7
0
p
F
The Timer/Event Counter 1 interrupt request flag (T1F),
external RC Oscillation Converter interrupt request flag
(RCOCF), A/D converter request flag (ADF), enable
Timer/Event Counter 1 interrupt bit (ET1I), enable exter-
nal RC Oscillation Converter interrupt bit (ERCOCI) and
enable A/D converter interrupt bit (EADI), form the inter-
rupt control register 1 (INTC1) which is located at ²1EH²
in the RAM.
S
Y
S
O
S
C
2
O
S
C
2
N
M
O
S
O
p
e
n
D
r
a
i
n
C
r
y
s
t
a
l
O
s
c
i
l
l
a
t
o
r
R
C
O
s
c
i
l
l
a
t
o
r
System Oscillator
Both are designed for system clocks, namely the RC os-
cillator and the Crystal oscillator, the choice of which is
determined by a configuration option. When the device
enters the Power Down Mode, the system oscillator will
stop running and will ignore external signals to conserve
power.
EMI, EEI0, EEI1, ET0I, ET1I, ERCOCI and EADI, are all
used to control the enable/disable status of interrupts.
These bits prevent the requested interrupt from being
serviced. Once the interrupt request flags, EIF0, EIF1,
T0F, T1F, RCOCF and ADF, are all set, they remain in
the INTC1 or INTC0 registers respectively until the inter-
rupts are serviced or cleared by a software instruction.
If an RC oscillator is used, an external resistor between
OSC1 and VDD is required to produce oscillation. The
resistance must range from 24kW to 1MW. The system
clock, divided by 4, is available on OSC2, which can be
used to synchronize external logic. The RC oscillator
provides the most cost effective solution, however, the
frequency of oscillation may vary with VDD, tempera-
tures and the device itself due to process variations. It is,
therefore, not suitable for timing sensitive operations
where an accurate oscillator frequency is desired.
It is recommended that a program does not use the
²CALL subroutine² within the interrupt subroutine. Inter-
rupts often occur in an unpredictable manner or need to
be serviced immediately in some applications. If only one
stack is left and enabling the interrupt is not well con-
trolled, the original control sequence may be damaged
once the ²CALL² is executed in the interrupt subroutine.
Rev. 1.00
12
December 13, 2006
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
