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CHAPTER 9 12-BIT PPG TIMER
9.1 Overview of 12-bit PPG Timer
The 12-bit PPG timer is a 12-bit binary counter, enabling the selection of one of four
types of internal count clocks. The timer is capable of setting a cycle period and "H"
width of output pulse waveforms and can also be used as a remote control
transmission frequency generator or 12-bit PPG.
■ Functions of 12-bit PPG Timer
• The timer generates a frequency for remote control and outputs signals to a PPG pin.
• The timer is capable of setting a cycle period and "H" width of output pulse waveforms separately.
• The timer enables the selection of a count clock from four types of internal clocks.
• The timer can generate a frequency in a range from twice to 2
12
-1 times as fast as the counter clock.
Table 9.1-1 lists the ranges in which the output pulse cycle period and "H" width are variable.
Note:
An example of calculating the output pulse cycle period and "H" width as executed by a 12-bit PPG
function is given below.
When an oscillation (F
CH
) of 12.5 MHz and a count clock cycle period of 2 t
INST
are set, and if:
Compare value for cycle period = 011110
B
(30-clock period)
Compare value for "H" width = 001010
B
(10-clock width)
Then, "H" width and the cycle period of output pulse waveforms are calculated as given below. These
calculations are obtained provided the system clock control register (SYCC) selects the fastest clock
(CS1, CS0 = 11
B
with one instruction cycle = 4/F
CH
).
Table 9.1-1 Ranges in which the Output Pulse Cycle Period and "H" Width are Variable
Internal count clock
cycle period
Output pulse cycle period Output pulse "H" width
2t
INST
4t
INST
to 8190t
INST
2t
INST
to 8188t
INST
4t
INST
8t
INST
to 16380t
INST
4t
INST
to 16376t
INST
16t
INST
32t
INST
to 65520t
INST
16t
INST
to 65504t
INST
256t
INST
512t
INST
to 1048.32kt
INST
256t
INST
to 1048.064kt
INST
t
INST:
Instruction cycle (to be affected by a gear function)