MITSUBISHI MICROCOMPUTERS
M37754M8C-XXXGP, M37754M8C-XXXHP
M37754S4CGP, M37754S4CHP
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
function as the 8-bit length pulse width modulator. The prescaler
(4) Pulse width modulation mode [11]
Figure 32 shows the bit configuration of the timer Ai mode register
during pulse width modulation mode. In pulse width modulation
mode, bits 0, 1, and 2 must be set to “1”.
counts the clock selected by bits 6 and 7. A pulse is generated
when the counter reaches 000016 as shown in Figure 34. At the
same time, the contents of the reload register is transferred to the
counter and count is continued.
Bit 5 is used to determine whether to perform 16-bit length pulse
width modulator or 8-bit length pulse width modulator. 16-bit length
pulse width modulator is selected when bit 5 is “0” and 8-bit length
pulse width modulator is selected when it is “1”. The 16-bit length
pulse width modulator is described first.
The pulse width modulator can be started with a software trigger or
with an input signal from a TAiIN pin (external trigger).
The software trigger mode is selected when bit 4 is “0”.
Pulse width modulator is started and a pulse is output from TAiOUT
when the timer Ai start bit is set to “1”.
Addresses
Timer A0 mode register
Timer A1 mode register
Timer A2 mode register
Timer A3 mode register
Timer A4 mode register
5616
5716
5816
5916
5A16
The external trigger mode is selected when bit 4 is “1”.
Pulse width modulation starts when a trigger signal is input from the
TAiIN pin when the timer Ai start bit is “1”. Whether to trigger at the
fall or rise of the trigger signal is determined by bit 3. The trigger is at
the fall of the trigger signal when bit 3 is “0” and at the rise when it is
“1”.
7
6
5
4
3
2
1
1
1
0
1
1 1 : Always “11” in pulse width modulation
mode
1 : Always “1” in pulse width modulation
mode
When data is written to timer Ai with the pulse width modulator
halted, it is written to the reload register and the counter.
Then when the timer Ai start bit is set to “1” and a software trigger or
an external trigger is issued to start modulation, the waveform shown
in Figure 33 is output continuously.
0 × : Software trigger
1 0 : Trigger at the falling of TAiIN input
1 1 : Trigger at the rising of TAiIN input
0 : 16-bit pulse width modulator
1 : 8-bit pulse width modulator
Once modulation is started, triggers are not accepted. If the value in
the reload register is m, the duration “H” of pulse is
Clock source select bit
0 0 : Select Pf2
0 1 : Select Pf16
1 0 : Select Pf64
1 1 : Select Pf512
1
× m
selected clock frequency
and the output pulse period is
1
× (216 –1).
selected clock frequency
An interrupt request signal is generated and the interrupt request bit
in the timer Ai interrupt control register is set at each fall of the output
pulse.
Fig. 32 Timer Ai mode register bit configuration during pulse width
modulation mode
The width of the output pulse is changed by updating timer data. The
update can be performed at any time. The output pulse width is
changed at the rise of the pulse after data is written to the timer.
The contents of the reload register are transferred to the counter just
before the rise of the next pulse so that the pulse width is changed
from the next output pulse.
Undefined data is read when timer Ai is read.
The 8-bit length pulse width modulator is described next.
The 8-bit length pulse width modulator is selected when the timer Ai
mode register bit 5 is “1”.
The reload register and the counter are both divided into 8-bit halves.
The low-order 8 bits function as a prescaler and the high-order 8 bits
31
RENESAS [ RENESAS TECHNOLOGY CORP ]
