4559 Datasheet, PDF (30/148 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4559 Group
TIMERS
The 4559 Group has the following timers.
• Programmable timer
The programmable timer has a reload register and enables the
frequency dividing ratio to be set. It is decremented from a
setting value n. When it underflows (count to n + 1), a timer
interrupt request flag is set to “1,” new data is loaded from the
reload register, and count continues (auto-reload function).
• Fixed dividing frequency timer
The fixed dividing frequency timer has the fixed frequency
dividing ratio (n). An interrupt request flag is set to “1” after
every n count of a count pulse.
FF16
n : Counter initial value
Count starts
Reload
n
1st underflow
Reload
2nd underflow
0016
Timer interrupt ^{“1”}
request flag ^{“0”}
Fig 32. Auto-reload function
n+1 count
n+1 count
Time
An interrupt occurs or
a skip instruction is executed.
Rev.1.04 Aug 23, 2007 Page 30 of 146
REJ03B0188-0104