Specifications

Counter/Timers
Mode 1 - Retriggerable One-Shot
In Mode 1, counter/timer 2 is triggered to generate a pulse of
programmed length. Applications can use this mode to signal the
occurrence of a single external event without having to monitor for a
change in count. This mode is supported only by counter/timer 2.
Examples of Mode 1 operation are shown in Figure 7-8. TOUT is
high until one clock pulse after TCTL triggers the count operation to
start. This is the start of the one-shot pulse. The pulse terminates by
lowering TOUT after the count reaches zero. TOUT remains low
until one clock pulse following the next TCTL trigger.
The Down Counter is armed after the Mode and Count are
programmed. A TCTL trigger transfers the count from the Count
register to the Down Counter and lowers TOUT on the next clock
pulse. This means an initial count of N results in a low level pulse
duration of N clock pulses. Since the one-shot is retriggerable, TOUT
remains low for N clock pulses after any trigger.
Programming the counter/timer with a new count does not affect the
current pulse width unless a TCTL trigger occurs. If this happens, the
new count is transferred to the Down Counter and the TOUT signal
remains low for the new number of programmed clock pulses.
7-18