![](http://datasheet.mmic.net.cn/30000/MR80C32-20-D_datasheet_2377239/MR80C32-20-D_113.png)
113
8154B–AVR–07/09
ATmega16A
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 Register (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 Cap-
ture 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
FigureIf 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
TCNT1H and TCNT1L –Timer/Counter1 High and Low Register
The two Timer/Counter I/O locations (TCNT1H and TCNT1L, combined TCNT1) give direct
access, both for read and for write operations, to the Timer/Counter unit 16-bit counter. To
Table 16-6.
Clock Select Bit Description
CS12
CS11
CS10
Description
0
No clock source (Timer/Counter stopped).
00
1
clk
I/O/1 (No prescaling)
01
0
clkI/O/8 (From prescaler)
01
1
clk
I/O/64 (From prescaler)
10
0
clk
I/O/256 (From prescaler)
10
1
clkI/O/1024 (From prescaler)
1
0
External clock source on T1 pin. Clock on falling edge.
1
External clock source on T1 pin. Clock on rising edge.
Bit
765
43
210
TCNT1[15:8]
TCNT1H
TCNT1[7:0]
TCNT1L
Read/Write
R/W
Initial Value
0