GMS81C2112 Datasheet, PDF (52/107 Pages) Hynix Semiconductor – HYNIX SEMICONDUCTOR 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C2112/GMS81C2120
8-bit Timer Mode
In the timer mode, the internal clock is used for counting
up. Thus, you can think of it as counting internal clock in-
put. The contents of TDRn are compared with the contents
of up-counter, Tn. If match is found, a timer 1 interrupt
(T1IF) is generated and the up-counter is cleared to 0.
Source clock
Start count
Up-counter
0
TDR1
T1IF interrupt
1
2
3
n
Counting up is resumed after the up-counter is cleared.
As the value of TDRn is changeable by software, time in-
terval is set as you want
n-2 n-1 n 0 1
2
3
4
Match Counter
Detect Clear
Figure 12-3 Timer Mode Timing Chart
Example: Make 2ms
interrupt using by Timer0 at 4MHz
LDM
LDM
SET1
EI
TM0,#0FH
TDR0,#125
T0E
; divide by 32
; 8us x 125= 1ms
; Enable Timer 0 Interrupt
; Enable Master Interrupt
When
TM0 = 0000 1111_B (8-bit Timer mode, Prescaler divide ratio = 32)
TDR0 = 125_D = 7D_H
f_XIN = 4 MHz
INTERRUPT PERIOD =
1
4 × 10⁶ Hz
× 32 × 125 = 1 ms
TDR1
7D
MATCH
(TDR0 = T0)
7D
7C
Count Pulse
Period
7B
~~
~~
up-count
7A
~~
8 µs
6
5
4
3
2
1
0
0
Timer 1 (T1IF)
Interrupt
Interrupt period
= 8 µs x 125
Occur interrupt
Occur interrupt
Occur interrupt
Figure 12-4 Timer Count Example
TIME
46
JUNE. 2001 Ver 1.00