MC68HC11E Motorola, MC68HC11E Datasheet - Page 143

• Manufacturer Part Number: MC68HC11E
• Description: Microcontrollers
• Manufacturer: Motorola

9.2 Timer Structure
M68HC11E Family — Rev. 5
MOTOROLA
The COP watchdog clock input (E ÷ 2
chain. The COP automatically times out unless it is serviced within a specific time
by a program reset sequence. If the COP is allowed to time out, a reset is
generated, which drives the RESET pin low to reset the MCU and the external
system. Refer to
Figure 9-2
control block includes logic for timer functions and for general-purpose I/O. For pins
PA3, PA2, PA1, and PA0, this block contains both the edge-detection logic and the
control logic that enables the selection of which edge triggers an input capture. The
digital level on PA[3:0] can be read at any time (read PORTA register), even if the
pin is being used for the input capture function. Pins PA[6:3] are used for either
general-purpose I/O, or as output compare pins. When one of these pins is being
used for an output compare function, it cannot be written directly as if it were a
general-purpose output. Each of the output compare functions (OC[5:2]) is related
to one of the port A output pins. Output compare one (OC1) has extra control logic,
allowing it optional control of any combination of the PA[7:3] pins. The PA7 pin can
be used as a general-purpose I/O pin, as an input to the pulse accumulator, or as
an OC1 output pin.
Control Bits
overflow —
overflow —
overflow —
overflow —
1 count —
1 count —
1 count —
1 count —
PR1, PR0
Freescale Semiconductor, Inc.
0 0
0 1
1 0
1 1
For More Information On This Product,
shows the capture/compare system block diagram. The port A pin
Table 9-1
Go to: www.freescale.com
65.536 ms
262.14 ms
524.29 ms
4.0 MHz
1.0 MHz
1000 ns
1000 ns
16.0 µs
1.049 s
4.0 µs
8.0 µs
Timing System
Table 9-1. Timer Summary
for crystal-related frequencies and periods.
32.768 ms
131.07 ms
262.14 ms
524.29 ms
8.0 MHz
2.0 MHz
15
500 ns
500 ns
Main Timer Count Rates
2.0 µs
4.0 µs
8.0 µs
) is tapped off of the free-running counter
XTAL Frequencies
21.845 ms
87.381 ms
174.76 ms
349.52 ms
12.0 MHz
1.333 µs
2.667 µs
5.333 µs
3.0 MHz
333 ns
333 ns
Timer Structure
Timing System
Other Rates
(E/2
(E/2
(E/2
(E/2
(E/16)
(1/E)
(E/1)
(E/4)
(E/8)
(E)
Data Sheet
16
18
19
20
)
)
)
)
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