80C186EC/80C188EC Microprocessor User's Manual

TIMER/COUNTER UNIT
9.3.2 Synchronization and Maximum Frequency
All timer inputs are latched and synchronized with the CPU clock. Because of the internal logic
required to synchronize the external signals, and the multiplexing of the counter element, the
Timer/Counter Unit can operate only up to ¼ of the CLKOUT frequency. Clocking at greater frequencies
will result in missed clocks.
9.3.2.1 Timer/Counter Unit Application Examples
The following examples are possible applications of the Timer/Counter Unit. They include a realtime
clock, a square wave generator and a digital one-shot.
9.3.3 Real-Time Clock
Example 9-1 contains sample code to configure Timer 2 to generate an interrupt request every 10
milliseconds. The CPU then increments memory-based clock variables.
9.3.4 Square-Wave Generator
A square-wave generator can be useful to act as a system clock tick. Example 9-2 illustrates how
to configure Timer 1 to operate this way.
9.3.5 Digital One-Shot
Example 9-3 configures Timer 1 to act as a digital one-shot.
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