Rainbow-electronics Atmega169L Manuel d'utilisateur télécharger pdf (Page 119)

119

ATmega169V/L

2514A–AVR–08/02

(ICF1), and this can be used to cause an Input Capture Interrupt, if this interrupt is

enabled.

When the ICR1 is used as TOP value (see description of the WGM13:0 bits located in

the TCCR1A and the TCCR1B Register), the ICP1 is disconnected and consequently

the Input Capture function is disabled.

• Bit 5 – Reserved Bit

This bit is reserved for future use. For ensuring compatibility with future devices, this bit

must be written to zero when TCCR1B is written.

• Bit 4:3 – WGM13:2: Waveform Generation Mode

See TCCR1A Register description.

• Bit 2:0 – CS12:0: Clock Select

The three Clock Select bits select the clock source to be used by the Timer/Counter, see

Figure 48 and Figure 49.

If external pin modes are used for the Timer/Counter1, transitions on the T1 pin will

clock the counter even if the pin is configured as an output. This feature allows software

control of the counting.

Timer/Counter1 Control

• Bit 7 – FOC1A: Force Output Compare for Channel A

• Bit 6 – FOC1B: Force Output Compare for Channel B

The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM

mode. However, for ensuring compatibility with future devices, these bits must be set to

zero when TCCR1A is written when operating in a PWM mode. When writing a logical

one to the FOC1A/FOC1B bit, an immediate compare match is forced on the Waveform

Generation unit. The OC1A/OC1B output is changed according to its COM1x1:0 bits

setting. Note that the FOC1A/FOC1B bits are implemented as strobes. Therefore it is

the value present in the COM1x1:0 bits that determine the effect of the forced compare.

Table 59. Clock Select Bit Description

CS12 CS11 CS10 Description

0 0 0 No clock source (Timer/Counter stopped).

001clk

I/O

/1 (No prescaling)

010clk

I/O

/8 (From prescaler)

011clk

I/O

/64 (From prescaler)

100clk

I/O

/256 (From prescaler)

101clk

I/O

/1024 (From prescaler)

1 1 0 External clock source on T1 pin. Clock on falling edge.

1 1 1 External clock source on T1 pin. Clock on rising edge.

Bit 7654 3 210

FOC1A FOC1B –– ––––TCCR1C

Read/Write R/W R/W R R R R R R

InitialValue0000 0000

1 2 ... 114 115 116 117 118 119 120 121 122 123 124 ... 316 317

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Rainbow-electronics Atmega169L Manuel d'utilisateur Page 119

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