Capture Mode - IBM EM78P809N Specification

Edge
Detector
INT3ES
TC3 pin
M
MUX
,
12 4
fc/2 fs/2
10 2
,
fc/2 fs/2
7
fc/2
TC2CK
2
TC3CR
4.10.1 Timer Mode:
In Timer mode, counting up is performed using the internal clock. When the contents of
the up-counter matched with the TCR3DA, then interrupt is generated and the counter
is cleared. Counting up resumes after the counter is cleared. The current contents of
the up-counter are loaded into the TCR3DB by setting TC3CAP to "1" and the TC3CAP
is cleared to "0" after capture automatically.
4.10.2 Counter Mode:
In Counter mode, counting up is performed using the external clock input pin (TC3 pin)
and either rising or falling edge can be selected by INT3ES0 but both edge cannot
be used. When the contents of the up-counter matched with the TCR3DA, then
interrupt is generated and the counter is cleared. Counting up resumes after the
counter is cleared. The current contents of the up-counter are loaded into the TCR3DB
by setting TC3CAP to "1" and the TC3CAP is cleared to "0" after capture automatically.
4.10.3

Capture mode:

In Capture mode, the pulse width, period and duty of the TC3 input pin are measured in
this mode, which can be used in decoding the remote control signal. The counter is
free running by the internal clock. On the rising (falling) edge of TC3 pin input, the
contents of the counter is loaded into TCR3DA, then the counter is cleared and
interrupt is generated. On the falling (rising) edge of TC3 pin input, the contents of the
counter are loaded into TCR3DB. The counter is still counting, on the next rising edge
of the TC3 pin input, the contents of the counter are loaded into TCR3A, counter is
Product Specification (V1.0) 07.26.2005
(This specification is subject to change without further notice)
Rising Inhibit
Capture
Falling
Control
TC3M
TC3S
CAP
Capture
TCR3B
Fig. 23. Configuration of Timer/Counter3
Overflow
8-bit Up-counter
Comparator
Capture
TCR3A
EM78P809N
8-Bit Microcontroller
TC3
Interrupt
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