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CHAPTER 16 8/16-BIT PPG
16.4
Operations of 8/16-bit PPG
One 8/16-bit PPG consists of two channels of 8-bit PPG units. These two channels can
be used in three modes: independent two-channel mode, 8-bit prescaler + 8-bit PPG
mode, and single-channel 16-bit PPG mode.
■ Operations of 8/16-bit PPG
Each of the 8-bit PPG units has two eight-bit reload registers. One reload register is for the "L" pulse width
(PRLL) and the other is for the "H" pulse width (PRLH). The values stored in these registers are reloaded
into the 8-bit down counter (PCNT), from the PRLL and PRLH in turn. The pin output value is inverted
upon a reload caused by counter borrow. This operation results in the pulses of the specified "L" pulse
width and "H" pulse width.
Table 16.4-1 lists the relationship between the reload operation and pulse outputs.
Table 16.4-1 Reload Operation and Pulse Output
Reload operation
PRLH → PCNT
PRLL → PCNT
When "1" is set in bit4 (PIE0) of PPGC0 or in bit12 (PIE1) of PPGC1, an interrupt request is output upon a
borrow from "00
■ Operation Modes of 8/16-bit PPG
This block can be used in three modes: independent two-channel mode, 8-bit prescaler + 8-bit PPG mode,
and single-channel 16-bit PPG mode.
●
Independent two-channel mode
The two channels of 8-bit PPG units operate independently. The PPG00 pin is connected to the ch.0 PPG
output, while the PPG10 pin is connected to the ch.1 PPG output.
●
8-bit prescaler + 8-bit PPG mode
Ch.0 is used as an 8-bit prescaler while the count in ch.1 is based on borrow outputs from ch.0. Thus, 8-bit
PPG waveforms can be output with arbitrary length of cycle time. The PPG00 pin is connected to the ch.0
prescaler output, while the PPG10 pin is connected to the ch.1 PPG output.
●
16-bit PPG 1ch mode
Ch.0 and ch.1 are connected and used as a single 16-bit PPG. The PPG00 and PPG10 pins are connected to
the 16-bit PPG output.
262
PPG0/PPG1 [0 → 1]
PPG0/PPG1 [1 → 0]
" to "FF
" (from "0000
H
H
H
Pin output change
" to "FFFF
" in 16-bit PPG mode) of each counter.
H
Rise
Fall
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