4552 Datasheet, PDF (65/145 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4552 Group
13 Prescaler and Timer 1 count start timing and count time when
operation starts
Count starts from the first rising edge of the count source (2) af-
ter Prescaler and Timer 1 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 1,
Timer 1 operates synchronizing with the falling edge of CNTR in-
put.
(2)
Count Source
Count Source
Selecting CNTR input
falling edge
Timer Value 3 2 1 0 3 2 1 0 3 2
Timer Underflow signal
(3)
(4)
(1) Timer Start
Fig. 62 Timer count start timing and count time when opera-
tion starts (Prescaler and Timer 1)
15 Watchdog timer
• The watchdog timer function is valid after system is released
from reset. When not using the watchdog timer function, execute
the DWDT instruction and the WRST instruction continuously,
and clear the WEF flag to “0” to stop the watchdog timer function.
• The watchdog timer function is valid after system is returned from
the power down state. When not using the watchdog timer func-
tion, execute the DWDT instruction and the WRST instruction
continuously every system is returned from the power down
state, and stop the watchdog timer function.
• When the watchdog timer function and power down function are
used at the same time, execute the WRST instruction before sys-
tem enters into the power down state and initialize the flag
WDF1.
16 Multifunction
• Be careful that the output of port D5 can be used even when INT
pin is selected.
The threshold value is different between port D5 and INT. Accord-
ingly, be careful when the input of both is used.
• Be careful that the “H” output of port C can be used even when
output of CNTR pin are selected.
17 Program counter
Make sure that the PCH does not specify after the last page of
the built-in ROM.
14 _{Timer 2 and Timer LC count start timing and count time when}
operation starts
Count starts from the rising edge (2) after the first falling edge of
the count source, after Timer 2 and Timer LC operations start (1).
Time to first underflow (3) is different from time among next un-
derflow (4) by the timing to start the timer and count source
operations after count starts.
(2)
Count Source
Timer Value
32 1 0 3 2 1 0 3
Timer Underflow Signal
(3)
(4)
(1) Timer Start
Fig. 63 Timer count start timing and count time when opera-
tion starts (Timer 2 and Timer LC)
Rev.3.02 Dec 22, 2006 page 65 of 142
REJ03B0023-0302