4507_M Datasheet, PDF (41/216 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 4500 SERIES

4507 Group
HARDWARE
FUNCTION BLOCK OPERATIONS
(8) Timer input/output pin (P12/CNTR pin)
CNTR pin is used to input the timer 2 count source and output the
timer 1 and timer 2 underflow signal divided by 2.
The P12/CNTR pin function can be selected by bit 0 of register W6.
The CNTR output signal can be selected by bit 1 of register W6.
When the CNTR input is selected for timer 2 count source, timer 2
counts the falling waveform of CNTR input.
(9) Precautions
Note the following for the use of timers.
•Prescaler
Stop the prescaler operation to change its frequency dividing ratio.
•Count source
Stop timer 1 or 2 counting to change its count source.
•Reading the count value
Stop timer 1 or 2 counting and then execute the TAB1 or TAB2 in-
struction to read its data.
•Writing to the timer
Stop timer 1 or 2 counting and then execute the T1AB or T2AB in-
struction to write its data.
•Writing to reload register R1
When writing data to reload register R1 while timer 1 is operating,
avoid a timing when timer 1 underflows.
CNTR input
Timer 2 count 0316
0216
0116
0016
(Note)
FF16
FE16
Timer 2 interrupt
request flag
(T2F)
Note: This is an example when “FF16” is set to timer 2 reload register R2L.
Fig. 23 Count timing diagram at CNTR input
• Timer 1 and timer 2 count start timing and count time when op-
eration starts
Count starts from the first rising edge of the count source (2) af-
ter timer 1 and timer 2 operations start (1).
Time to first underflow (3) is shorter (for up to 1 period of the
count source) than time among next underflow (4) by the timing
to start the timer and count source operations after count starts.
When selecting CNTR input as the count source of timer 2, timer
2 operates synchronizing with the falling edge of CNTR input.
Count Source
Count Source
(CNTR input)
Timer Value
(2)
32 1 0 3 2 1 0 3 2
Timer Underflow
Signal
(3)
(4)
(1) Timer
Fig. 24 Timer count start timing and count time when opera-
tion starts (T1, T2)
Rev.2.01 Feb 04, 2005
REJ09B0195-0201
1-29