Rev.3.02
Apr 10, 2008
REJ03B0177-0302
38D2 Group
Frequency Divider For Timer
Each timer X and timer Y have the frequency dividers for the
count source. The count source of the frequency divider is
switched to XIN, XCIN, or the on-chip oscillator OCO divided by
4 in the on-chip oscillator mode by the CPU mode register. The
division ratio of each timer can be controlled by each timer
division ratio selection bit. The division ratio can be selected
from as follows;
1/1, 1/2, 1/16, 1/256 of f(XIN), f(XCIN) or f(OCO)/4.
Switch the frequency division or count source* while the timer
count is stopped.
*This also applies when the frequency divider output is selected
as the timer count source and the count source is switched in
conjunction with a transition between operating modes (on-
chip oscillator mode, XIN mode, or low-speed mode). Be
careful when changing settings in the CPU mode register.
Timer X
The count source for timer X can be set using the timer X mode
register. XCIN may be selected as the count source. If XCIN is
selected, count operation is possible regardless of whether or not
the XIN input oscillator or the on-chip oscillator is operating.
The timer X operates as down-count. When the timer contents
reach “000016”, an underflow occurs at the next count pulse and
the timer latch contents are reloaded. After that, the timer
continues countdown. When the timer underflows, the interrupt
request bit corresponding to the timer X is set to “1”.
Six operating modes can be selected for timer X by the timer X
mode register and timer X control register.
(1) Timer Mode
The count source can be selected by setting the timer X mode
register. In this mode, timer X operates as the 18-bit counter by
setting the timer X register (extension).
(2) Pulse Output Mode
Pulses of which polarity is inverted each time the timer
underflows are output from the TXOUT1 pin. Except for that, this
mode operates just as in the timer mode.
When using this mode, set the port sharing the TXOUT1 pin to
output mode.
(3) IGBT Output Mode
After dummy output from the TXOUT1 pin, count starts with the
INT0 pin input as a trigger. In the case that the timer X output 1
active edge switch bit is “0”, when the trigger is detected or the
timer X underflows, “H” is output from the TXOUT1 pin. And
then, when the count value corresponds with the compare
register 1 value, the TXOUT1 output becomes “L”.
After noise is cleared by noise filters, judging continuous 4-time
same levels with sampling clocks to be signals, the INT0 signal
can use 4 types of delay time by a delay circuit.
When using this mode, set the port sharing the INT0 pin to input
mode and set the port sharing the pin used as TXOUT1 or TXOUT2
function to output mode.
When the timer X output control bit 1 or 2 of the timer X control
register is set to “1”, the timer X count stop bit is fixed to “1”
forcibly by the interrupt signal of INT1 or INT2. And then, the
TXOUT1 output and TXOUT2 output can be set to “L” forcibly at
the same time that the timer X stops counting.
Do not write “1” to the timer X register (extension) when using
the IGBT output mode.
(4) PWM Mode
IGBT dummy output, an external trigger with the INT0 pin and
output control with pins INT1 and INT2 are not used. Except for
those, this mode operates just as in the IGBT output mode.
The period of PWM waveform is specified by the timer X set
value. In the case that the timer X output 1 active edge switch bit
is “0”, the “H” interval is specified by the compare register 1 set
value. In the case that the timer X output 2 active edge switch bit
is “0”, the “H” interval is specified by the compare registers 2
and 3 set values.
When using this mode, set the port sharing the pin used as
TXOUT1 or TXOUT2 function to output mode.
Do not write “1” to the timer X register (extension) when using
the PWM mode.
(5) Event Counter Mode
The timer counts signals input through the CNTR0 pin. In this
mode, timer X operates as the 18-bit counter by setting the timer
X register (extension). When using this mode, set the port
sharing the CNTR0 pin to input mode.
In this mode, the window control can be performed by the timer
1 underflow. When the bit 5 (data for control of event counter
window) of the timer X mode register is set to “1”, counting is
stopped at the next timer 1 underflow. When the bit is set to “0”,
counting is restarted at the next timer 1 underflow.
(6) Pulse Width Measurement Mode
In this mode, the count source is the output of frequency divider
for timer. In this mode, timer X operates as the 18-bit counter by
setting the timer X register (extension). When the bit 6 of the
CNTR0 active edge switch bits is “0”, counting is executed
during the “H” interval of CNTR0 pin input. When the bit is “1”,
counting is executed during the “L” interval of CNTR0 pin input.
When using this mode, set the port sharing the CNTR0 pin to
input mode.
Also, set to enable (“0”) the data for control of event counter
window (bit 5 of timer X mode register (address 002D16)).