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CHAPTER 7 8-BIT PWM TIMER
7.5
Operation of Interval Timer Function
This section describes the operation of the interval timer function of the 8-bit PWM
timer.
I Operation of interval timer function
Figure 7.5-1 "Interval timer function settings" shows the settings required to operate as an interval timer
function.
CNTR
COMR
On activation, the counter starts to count up from "00
When the counter value matches the value set in the COMR register (compare value), the PWM timer
inverts the level of the output pin (PWM) on the next rising edge of the count clock, clears the counter, sets
the interrupt request flag bit (CNTR: TIR = "1"), and restarts counting from "00
Figure 7.5-2 "Operation of 8-bit PWM timer" shows the operation of the 8-bit PWM timer.
Counter value
COMR value (FF
TIR bit
TPE bit
OE bit
PWM pin
When the output pin control bit (OE) is "0", the pin operates as a general-purpose I/O port (P41).
*: If the PWM compare register (COMR) value is modified during counter operation, the new value will be effective in next cycle.
132
Figure 7.5-1 Interval timer function settings
Bit 7
Bit 6
Bit 5
P/T
0
Sets interval time (compare value).
Figure 7.5-2 Operation of 8-bit PWM timer
Compare value (FF
FF
H
80
H
00
H
Timer cycle
COMR value modified (FF
)
H
Cleared by the program
Bit 4
Bit 3
Bit 2
P1
P0
TPE
TIR
1
" on the rising edge of the selected count clock.
H
)
Compare value (80
H
80
H
H
Bit 1
Bit 0
OE
TIE
: Used bit
1 : Set "1".
0 : Set "0".
".
H
)
H
Time
)*
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