Chapter 7
16-bit Timers
VII - 40
16-bit High Precision PWM Output
(5)
Select fosc as the clock source by the
TM7CK1-0 flag of the TM7MD1 register. Also,
select 1/2 dividing as count clock source by the
TM7PS1-0 flag.
(6)
Set the PWM output cycle to the timer 7 preset
register 1 (TM7PR1). To be 400 Hz by dividing
10 MHz, set as follows:
25000 - 1 = 24999 (x'61a7')
At that time, the same value is loaded to the
timer 7 compare register 1 (TM7OC1), and the
timer 7 binary counter (TM7BC) is initialized to
x'0000'.
(7)
Set the "H" period of the PWM output to the
timer 7 preset register 2 (TM7PR2). To be a
1/4 duty of 25000 dividing, set as follows:
25000 / 4 = 6250 (x'186a')
At that time, the same value is loaded to the
timer 7 compare register 2 (TM7OC2).
(8)
Set the TM7EN flag of the TM7MD1 register to
"1" to start timer 7.
Setup Procedure
(5)
Select the count clock source.
TM7MD1 (x'3F78')
bp1-0
: TM7CK1-0 = 00
bp3-2
: TM7PS1-0 = 01
(6)
Set the PWM output cycle.
TM7PR1 (x'3F75',x'3F74') = x'61a7'
(7)
Set the "H" period of the PWM
output.
TM7PR2 (x'3F7D',x'3F7C')=x'186a'
(8)
Start the timer operation.
TM7MD1 (x'3F78')
bp4
: TM7EN
= 1
Description
TM7BC counts up from x'0000'. The PWM source waveform outputs "H" until TM7BC matches the
set value of the TM7OC2 register. Once they matches, it outputs "L". After that, TM7BC continues to
count up. Once TM7BC matches the TM7OC1 register to be cleared, the PWM source waveform
outputs "H" again and TM7BC counts up from x'0000' again. TM7IO pin outputs one count clock
delay of the PWM source waveform.
To output the timer pulse output from the TM7O large current pin, set the P5OMD1 flag of the port
5 output mode register (P5OMD) at the setup example(2), to "1" to set the P51 pin as a special
function pin, and set the P5DIR1 flag of the port 5 direction control register to "1" to set output mode.
Set as the set value of TMnOC2
≤ the set value of TMnOC1. If it is set as the set value of
TMnOC2 > the set value of TMnOC1, the PWM output is a "H" fixed output.
In the initial state of the PWM output, it is changed to "H" output from "L" output at the timing
that the PWM operation is selected with the TM7OUT1-0 flag of the TM7MD3 register.
As for timer 8, it can be selected with the TN8PWMF flag of TM8MD3.