Datasheet

131
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
• Bit 6 – ICES1: Input Capture Edge Select
This bit selects which edge on the Input Capture pin (ICP1) that is used to trigger a capture event. When the ICES1
bit is written to zero, a falling (negative) edge is used as trigger, and when the ICES1 bit is written to one, a rising
(positive) edge will trigger the capture.
When a capture is triggered according to the ICES1 setting, the counter value is copied into the Input Capture Reg-
ister (ICR1). The event will also set the Input Capture Flag (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 16-10 on page 127
and Figure 16-11 on page 127.
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.
16.11.3 TCCR1C – Timer/Counter1 Control Register C
• Bit 7 – FOC1A: Force Output Compare for Unit A
• Bit 6 – FOC1B: Force Output Compare for Unit B
The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM mode. However, for ensur-
ing 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
Figure 16-14. 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 3210
(0x82) FOC1A FOC1B
– – – – – – TCCR1C
Read/Write R/W R/W R R R R R R
Initial Value 0 0 0 0 0 0 0 0