8 Main Timer
The main timer is based on a free-running 16-bit counter with a four-stage programmable prescaler. A
timer overflow function allows software to extend the system's timing capability beyond the counter's
16-bit range.
The timer has three channels of input capture and five channels of output compare.
Refer to the following table for a summary of crystal-related frequencies and periods.
Table 6 Timer Summary
XTAL Frequencies
4.0 MHz
1.0 MHz
1000 ns
8.0 MHz
2.0 MHz
500 ns
12.0 MHz
3.0 MHz
333 ns
Other Rates
(E)
Control
Bits
(1/E)
PR[1:0]
Main Timer Count Rates
0 0
1 count —
overflow —
1.0 µs
65.536 ms
500 ns
32.768 ms
333 ns
21.845 ms
(E/1)
16
(E/2
)
)
)
0 1
1 count —
overflow —
4.0 µs
262.14 ms
2.0 µs
131.07 ms
1.333 µs
87.381 ms
(E/4)
18
(E/2
1 0
1 count —
overflow —
8.0 µs
524.29 ms
4.0 µs
262.14 ms
2.667 µs
174.76 ms
(E/8)
19
(E/2
1 1
1 count —
overflow —
16.0 µs
1.049 s
8.0 µs
524.29 ms
5.333 µs
349.52 ms
(E/16)
20
(E/2
)
RTR[1:0]
Periodic (RTI) Interrupt Rates
13
14
15
16
0 0
0 1
1 0
1 1
8.192 ms
16.384 ms
32.768 ms
65.536 ms
4.096 ms
8.192 ms
16.384 ms
32.768 ms
2.731 ms
5.461 ms
10.923 ms
21.845 ms
(E/2
(E/2
(E/2
(E/2
)
)
)
)
MOTOROLA
32
MC68HC11A8
MC68HC11A8TS/D
MOTOROLA [ MOTOROLA ]
