Operations Of 8/16-Bit Ppg Timer - Fujitsu F2MC-16LX Hardware Manual

CHAPTER 17 8/16-BIT PPG TIMER

17.3 Operations of 8/16-Bit PPG Timer

The 8/16-bit PPG timer contains an 8-bit PPG unit for six channels (PPG0/1,PPG2/
3,PPG4/5). In addition to independent operation, the channels can also be used in
direct connection mode (PPG0 is used in combination with PPG1, PPG2 is used in
combination with PPG3, and PPG4 is used in combination with PPG5). In total, three
types of operation are therefore supported: independent operation, 8-bit prescaler/8-
bit PPG mode, and 16-bit PPG mode.
I Outline of 8/16-bit PPG timer operation
Each 8-bit PPG unit has two 8-bit reload registers, one L-side and one H-side register (PRLL,
PRLH).
The values in these registers are reloaded into the corresponding L/H sides of the 8-bit down
counter (PCNT), and decremented at every clock pulse. The value of the output pin is inverted
at reloading when a counter borrow occurs. This operation ensures that the output pin outputs
pulses with an L/H width that corresponds to the reload register values.
Operation start or restart are initiated by setting the corresponding bit in the register.
The relationship between the reload operation and pulse output is shown below.
Reload operation
PRLH --> PCNT
If bit 4 of PPGC0 (PIE0) is set to "1" and bit 2 of PPGC1 (PIE1) is set to "1", a 00 to FF counter
borrow for each counter (in 16-bit PPG mode, a 0000 to FFFF counter borrow) will cause an
interrupt request.
I Operation mode
The 8/16-bit PPG timer has three operation modes: two-channel independent mode, 8-bit
prescaler/8-bit PPG mode, and 16-bit PPG mode (the MB90470 has three channels per mode).
Two-channel independent mode allows the two channels to be used independently as 8-bit
PPGs. The PPG0 pin is connected to the output of channel 0, and the PPG1 pin is connected to
the output of channel 1 (PPG2 to PPG5 correspond to channels 2 to 5).
8-bit prescaler/8-bit PPG mode is a mode in which channel 0 (channel 2 or channel 4) operates
as bit prescaler, while channel 1 (channel 3 or channel 5) is counted with a borrow output of
channel 0 (channel 2 or channel 4), which allows an 8-bit PPG waveform of an arbitrary interval
to be output. The PPG0 (PPG2 or PPG4) pin is connected with the prescaler output of channel
0 (channel 2 or channel 4), and the PPG1 pin (PPG3, or PPG5) is connected with the PPG
output of channel 1 (channel 3 or channel 5).
16-bit PPG1 channel mode (the MB90470 has 3 channels) is an operation mode in which
channel 0 and channel 1 are directly connected (direct connection between channels 2 and 3
respectively with channels 4 and 5) to allow 16-bit PPG operation. Both PPG 0 and PPG1 are
connected with the 16-bit PPG output.
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Pin output change
PPG0/1[0 --> 1] rising