C515C Datasheet, PDF (33/69 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C515C
Timer / Counter 0 and 1
Timer/Counter 0 and 1 can be used in four operating modes as listed in table 6 :
Table 6
Timer/Counter 0 and 1 Operating Modes
Mode Description
0
8-bit timer/counter with a
divide-by-32 prescaler
1
16-bit timer/counter
2
8-bit timer/counter with
8-bit autoreload
3
Timer/counter 0 used as one
8-bit timer/counter and one
8-bit timer / Timer 1 stops
TMOD
M1 M0
0
0
0
1
1
0
1
1
Timer/Counter Input Clock
internal
external (max)
f_OSC/6 x 32
f_OSC/12 x 32
f_OSC/6
f_OSC/12
In the “timer” function (C/T = ‘0’) the register is incremented every machine cycle. Therefore the
count rate is f_OSC/6.
In the “counter” function the register is incremented in response to a 1-to-0 transition at its
corresponding external input pin (P3.4/T0, P3.5/T1). Since it takes two machine cycles to detect a
falling edge the max. count rate is f_OSC/12. External inputs INT0 and INT1 (P3.2, P3.3) can be
programmed to function as a gate to facilitate pulse width measurements. Figure 11 illustrates the
input clock logic
OSC
P3.4/T0
P3.5/T1
Gate
=1
(TMOD)
P3.2/INT0
P3.3/INT1
÷6
C/T = 0
C/T = 1
TR0
TR1
&
<_ 1
f _OSC/6
Timer 0/1
Input Clock
Control
MCS03117
Figure 11
Timer/Counter 0 and 1 Input Clock Logic
Semiconductor Group
33
1997-07-01