HYUNDAI MicroElectronics
8-bit Timer Mode
GMS82512/16/24
Maximum Time
Setting
(At fXIN=8 M Hz)
Resolution
Valueof Clock
TM[1:0] Source
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.
Counting up is resumed after the up-counter is cleared.
(At fXIN=8 MHz)
1/fEC1
sec
1/fEC1 × 256
fEC1
00
01
10
11
sec
f
f
f
XIN ÷ 4
us
us
us
us
us
us
0.5
2
128
512
XIN ÷ 16
XIN ÷ 64
8
2048
As the value of TDRn is changeable by software, time in-
terval is set as you wantꢂ
Table 11-1 Timer Source clock Interrupt Time
Start count
Source clock
2
3
n-2
n-1
n
1
4
2
3
0
1
0
Up-counter
n
TDR1
Match
Detect
Counter
Clear
T1IF interrupt
Figure 11-4 Timer Mode Timing Chart
Example:
Make 1msꢁinterrupt using by Timer0 at 8MHz
LDM
LDM
TM0,#1FH
; divide by 64
TDR0,#125
; 8us x 125= 1ms
SET1 T0E
EI
; Enable Timer 0 Interrupt
; Enable Master Interrupt
When
TM0 = 0001 1111 (8-bit Timer mode, Prescaler divide ratio = 64)
B
TDR0 = 125 = 7D
D
H
f
= 8 MHz
XIN
1
INTERRUPT PERIOD =
× 64 × 125 = 1 ms
8 × 106 Hz
TDR1
7D
MATCH
(TDR0 = T0)
Count Pulse
Period
7D
7C
7B
7A
8 µs
6
5
4
3
2
1
0
0
TIME
Interrupt period
= 8 µs x 125
Timer 1 (T1IF)
Interrupt
Occur interrupt
Occur interrupt
Occur interrupt
Figure 11-5 Timer Count Example
FEB. 2000 Ver 1.00
37
HYNIX [ HYNIX SEMICONDUCTOR ]
