MC68HC705JP7 Datasheet, PDF (165/242 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Programmable Timer
Input Capture Registers
Address: $001A
Bit 7
6
5
4
3
2
Read: Bit 15
14
13
12
11
10
Write:
Reset: 1
1
1
1
1
1
1
Bit 0
9
Bit 8
1
1
Address: $001B
Bit 7
6
5
4
3
2
1
Bit 0
Read: Bit 7
6
5
4
3
2
1
Bit 0
Write:
Reset: 1
1
1
1
1
1
0
0
= Unimplemented
Figure 11-5. Alternate Counter Registers (ACRH and ACRL)
11.5 Input Capture Registers
The input capture function is a means to record the time at which an
event occurs. The source of the event can be the change on an external
pin (PB3/AN3/TCAP) or the CPF2 flag bit of voltage comparator 2 in the
analog subsystem. The ICEN bit in the analog subsystem control
register (ACR) at $001D selects which source is the input signal. When
the input capture circuitry detects an active edge on the selected source,
it latches the contents of the free-running timer counter registers into the
input capture registers as shown in Figure 11-6.
NOTE: Both the ICEN bit in the ACR and the IEDG bit in the TCR must be set
when using voltage comparator 2 to trigger the input capture function.
Latching values into the input capture registers at successive edges of
the same polarity measures the period of the selected input signal.
Latching the counter values at successive edges of opposite polarity
measures the pulse width of the signal.
MC68HC705JJ7 • MC68HC705JP7 — REV 4
MOTOROLA
Programmable Timer
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