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CHAPTER 15 8/16-BIT PPG TIMER
15.3 Operation of 8/16-bit PPG Timer
■ Count Clock Selection
The count clock used for 8/16-bit PPG timer operation uses the peripheral clock and the time-base counter
input to allow 6 types of count clock input selection.
The bit4 to bit2 (PCM2 to PCM0) of PPG01/PPG23 register selects the ch.0 (ch.2) clock and the bit7 to
bit5 (PCS2 to PCS0) of PPG01/PPG23 register selects the ch.1 (ch.3) clock.
For the clock selection, 1/16 to 1 times of machine clock and the time-base counter input are selected.
Notes:
•
The PCS2 to PCS0 value of PPG01/PPG23 register is invalid in the 8-bit prescaler + 8-bit PPG
mode and 16-bit PPG mode.
•
When the time-base timer input is used, the trigger or the first count cycle after stopping may
deviate. In addition, if the time-base counter is initialized in the 8/16-bit PPG timer operation, the
cycle may deviate.
•
When the ch.0/ch.2 is in the operating status, the ch.1/ch.3 is in the stopped status, and the ch.1
(ch.3) is started in the 8-bit prescaler + 8-bit PPG mode, the first count cycle may deviate.
■ Pin Output Control of Pulse
The pulse generated by the 8/16-bit PPG timer can be output from the external pins (PPG0 to PPG3). To
output pulses from the external pin, "1" is written in the bit corresponding to each pin. The PPGC0 bit5
(PE00) and the PPGC1 bit13 (PE10) are used for the PPG0/PPG2 and PPG1/PPG3 pins, respectively.
When "0" is written in this pin (initial value), no pulse is output from the external pin that then functions as
a general-purpose port.
Since the same waveform is output from the PPG0 to PPG3 in the 16-bit PPG mode, either of external pins
can be enabled to obtain the same output.
The 8-bit prescaler toggle waveform and the 8-bit PPG waveform are output from the PPG0/PPG2 and the
PPG1/PPG3, respectively, in the 8-bit prescaler + 8-bit PPG mode.
The output waveform in this mode is shown in Figure 15.3-2.
Figure 15.3-2 The 8-bit Prescaler + 8-bit PPG Mode Output Operation Waveform
P
PPG0
PPG1
354
0
P
0
H
L
P
1
H
FUJITSU MICROELECTRONICS LIMITED
MB90335 Series
P
1
L
CM44-10137-6E
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