HD404369F datasheet(67/117 Pages) RENESAS

67 / 117 page

HD404369 Series

Timer C Operations:

• Free-running/reload timer operation: The free-running/reload operation, input clock source, and

prescaler division ratio are selected by timer mode register C (TMC: $00D).

Timer C is initialized to the value set in timer write register C (TWCL: $00E, TWCU: $00F) by

software and incremented by one at each clock input. If an input clock is applied to timer C after it has

reached $FF, an overflow is generated. In this case, if the reload timer function is enabled, timer C is

initialized to its initial value set in timer write register C; if the free-running timer function is enabled,

the timer is initialized to $00 and then incremented again.

The overflow sets the timer C interrupt request flag (IFTC: $002, bit 2). IFTC is reset by software or

MCU reset. Refer to figure 3 and table 1 for details.

• Watchdog timer operation: Timer C is used as a watchdog timer for detecting out-of-control program

routines by setting the watchdog on flag (WDON: $020, bit 1) to 1. If a program routine runs out of

control and an overflow is generated, the MCU is reset. The watchdog timer operation flowchart is

shown in figure 48. Program run can be controlled by initializing timer C by software before it reaches

$FF.

• Timer output operation: The PWM output modes can be selected for timer C by setting port mode

By selecting the timer output mode, pin R0

3/TOC is set to TOC. The output from TOC is reset low by

MCU reset.

PWM output: When PWM output mode is selected, timer C provides the variable-duty pulse output

function. The output waveform differs depending on the contents of timer mode register C (TMC:

$00D) and timer write register C (TWCL: $00E, TWCU: $00F). The output waveform is shown in

figure 49.

$FF + 1

$00

Timer C

count value

Overflow

Time

CPU

operation

Normal

operation

Timer C

clear

Normal

operation

Timer C

clear

Program

runaway

Normal

operation

Reset

Figure 48 Watchdog Timer Operation Flowchart

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