R8C/20 Group, R8C/21 Group 14. Timers
Rev.2.00 Aug 27, 2008 Page 143 of 458
REJ09B0250-0200
Figure 14.18 Operating Example of Timer RB when Counter Value is Rewritten during Count
Operation
Count source
Reloads register of
timer RB prescaler
IR bit in TRBIC
register
0
Counter of
timer RB prescaler
Reloads register of
timer RB
Counter of timer RB
Set 01h to the TRBPRE register and 25h to
the TRBPR register by a program.
After writing, the reload register is
written with the first count source.
Reload with
the second
count source
Reload on
underflow
After writing, the reload register is
written on the first underflow.
Reload on the second
underflow
The IR bit remains unchanged until underflow
is generated by a new value.
When the TWRC bit is set to 0 (write to reload register and counter)
Count source
Reloads register of
timer RB prescaler
IR bit in TRBIC
register
Counter of
timer RB prescaler
Reloads register of
timer RB
Counter of timer RB
Set 01h to the TRBPRE register and 25h to
the TRBPR register by a program.
After writing, the reload register is
written with the first count source.
Reload on
underflow
After writing, the reload register is
written on the first underflow.
Reload on
underflow
Only the prescaler values are updated,
extending the duration until timer RB underflow.
When the TWRC bit is set to 1 (write to reload register only)
05h 04h 03h 02h 01h 00h 01h 00h 01h 00h06h 01h 00h 01h
03h 00h02h 01h 25h
New value (25h)Previous value
New value (01h)Previous value
New value (01h)Previous value
05h 04h 01h 00h 01h 00h 01h 00h 01h 00h06h
New value (25h)Previous value
03h 24h02h 25h
The above applies under the following conditions.
Both bits TSTART and TCSTF in the TRBCR register are set to 1 (During count).
0
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