16-Bit Reload Timer Operation - Fujitsu MB91319 Series Hardware Manual

5.3

16-bit Reload Timer Operation

This section describes the following operations of the 16-bit reload timer:
• Internal clock operation
• Underflow operation
• Operation of the input pin function
• Operation of the output pin function
■ Internal Clock Operation
If the timer operates with a divide-by clock of the internal clock, one of the clocks created by
dividing the machine clock by 2, 8, or 32 can be selected as the clock source.
The external input pin can be used as the trigger or gate input depending on the register setting.
To start the count operation as soon as counting is enabled, write "1" to the CNTE and TRG bits
of the control status register. Trigger input occurring due to the TRG bit is always valid regardless
of the operating mode while the timer is running (CNTE=1).
Figure 5.3-1 shows the startup and operations of the counter.
Time as long as T (T: peripheral clock machine cycle) is required after the counter start trigger is
input and before the data of the reload register is actually loaded into the counter.
Count clock
Counter
Data load
CNTE (register)
TRG (register)
Figure 5.3-1 Startup and Operations of the Counter
Reload data
T
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