TMP91C824
91C824-102
2008-02-20
3.7.4
Operation in Each Mode
(1)
8-bit timer mode
Both TMRA0 and TMRA1 can be used independently as 8-bit interval timers.
Setting its function or counter data for TMRA0 and TMRA1 after stop these
registers.
a. Generating interrupts at a fixed interval (using TMRA1)
To generate interrupts at constant intervals using TMRA1 (INTTA1), first stop
TMRA1 then set the operation mode, input clock and a cycle to TA01MOD and
TA1REG register, respectively. Then, enable the interrupt INTTA1 and start
TMRA1 counting.
Example: To generate an INTTA1 interrupt every 10
µ
seconds at fc
=
33 MHz, set
each register as follows:
*
Clock state
System clock: High frequency (fc)
Prescaler clock: f
FPH
MSB
LSB
7 6 5 4 3
2
1
0
TA01RUN
← −
X X X
−
−
0
−
Stop TMRA1 and clear it to 0.
TA01MOD
←
0 0 X X 1
0
X
X
Select 8-bit timer mode and select
φ
T1
((2
3
/fc)s at fc
=
33 MHz) as the input clock.
TA1REG
←
0 0 1 0 1
0
0
0
Set TA1REG to 10
µ
s
÷
φ
T1 (2
3
/fc)s
≈
40
=
28H.
INTETA01
← −
1 0 1
−
−
−
−
Enable INTTA1 and set it to level 5.
TA01RUN
← −
X X X
−
1
1
−
Start
TMRA1
counting.
X: Don’t care,
−
: No change
Select the input clock using in Table 3.7.2.
Note: The input clocks for TMRA0 and TMRA1 are different from as follows.
TMRA0: TA0IN input,
φ
T1,
φ
T4 or
φ
T16
TMRA1: Match output of TMRA0,
φ
T1,
φ
T16,
φ
T256