
1997 Intermediate Version
Semiconductor Group
19
1997-10-01
C163-16F
In addition to their basic operating modes, timers T2 and T4 may be configured as reload or capture
registers for timer T3. When used as capture or reload registers, timers T2 and T4 are stopped. The
contents of timer T3 is captured into T2 or T4 in response to a signal at their associated input pins
(TxIN). Timer T3 is reloaded with the contents of T2 or T4 triggered either by an external signal or
by a selectable state transition of its toggle latch T3OTL. When both T2 and T4 are configured to
alternately reload T3 on opposite state transitions of T3OTL with the low and high times of a PWM
signal, this signal can be constantly generated without software intervention.
Figure 6
Block Diagram of GPT2
With its maximum resolution of 160 ns (@ 25 MHz), the GPT2 module provides precise event
control and time measurement. It includes two timers (T5, T6) and a capture/reload register
(CAPREL). Both timers can be clocked with an input clock which is derived from the CPU clock via
a programmable prescaler or with external signals. The count direction (up/down) for each timer is
programmable by software or may additionally be altered dynamically by an external signal on a
port pin (TxEUD). Timer T6 has an output toggle latch (T6OTL) which changes its state on each
timer overflow/underflow. Concatenation of the timers is supported via T6OTL.
The state of this latch may be used to clock timer T5, or it may be output on a port pin (T6OUT). The
overflows/underflows of timer T6 can additionally be used to clock the CAPCOM timers T0 or T1,
and to cause a reload from the CAPREL register. The CAPREL register may capture the contents
of timer T5 based on an external signal transition on the corresponding port pin (CAPIN), and timer
T5 may optionally be cleared after the capture procedure. This allows absolute time differences to
be measured or pulse multiplication to be performed without software overhead.