at94k40al ATMEL Corporation, at94k40al Datasheet - Page 104

• Manufacturer Part Number: at94k40al
• Description: At94kal Series Field Programmable System Level Integrated Circuit
• Manufacturer: ATMEL Corporation

104
AT94KAL Series FPSLIC
Timer/Counter1 Control Register B – TCCR1B
• Bit 7 - ICNC1: Input Capture1 Noise Canceler (4 CKs)
When the ICNC1 bit is cleared (zero), the input capture trigger noise canceler function is dis-
abled. The input capture is triggered at the first rising/falling edge sampled on the PE7(ICP) –
input capture pin – as specified. When the ICNC1 bit is set (one), four successive samples are
measured on the PE7(ICP) – input capture pin, and all samples must be High/Low according to
the input capture trigger specification in the ICES1 bit. The actual sampling frequency is XTAL
clock frequency.
• Bit 6 - ICES1: Input Capture1 Edge Select
While the ICES1 bit is cleared (zero), the Timer/Counter1 contents are transferred to the Input
Capture Register – ICR1 – on the falling edge of the input capture pin – PE7(ICP). While the
ICES1 bit is set (one), the Timer/Counter1 contents are transferred to the Input Capture Register
– ICR1 – on the rising edge of the input capture pin – PE7(ICP).
• Bit 5 - ICPE: Input Captive Pin Enable
This bit must be set by the user to enable the Input Capture Function of timer1. Disabling pre-
vents unnecessary register copies during normal use of the PE7 port.
• Bit 4 - Res: Reserved Bit
This bit is reserved in the FPSLIC and will always read zero.
• Bit 3 - CTC1: Clear Timer/Counter1 on Compare Match
When the CTC1 control bit is set (one), the Timer/Counter1 is reset to $0000 in the clock cycle
after a compareA match. If the CTC1 control bit is cleared, Timer/Counter1 continues counting
and is unaffected by a compare match. When a prescaling of 1 is used, and the compareA reg-
ister is set to C, the timer will count as follows if CTC1 is set:
... | C-1 | C | 0 | 1 | ...
When the prescaler is set to divide by 8, the timer will count like this:
... | C-1, C-1, C-1, C-1, C-1, C-1, C-1, C-1 | C, C, C, C, C, C, C, C | 0, 0, 0, 0, 0, 0, 0, 0 | ...
In PWM mode, this bit has a different function. If the CTC1 bit is cleared in PWM mode, the
Timer/Counter1 acts as an up/down counter. If the CTC1 bit is set (one), the Timer/Counter
wraps when it reaches the TOP value. Refer to
• Bits 2,1,0 - CS12, CS11, CS10: Clock Select1, Bits 2, 1 and 0
The Clock Select1 bits 2,1 and 0 define the prescaling source of Timer/Counter1.
Bit
$2E ($4E)
Read/Write
Initial Value
7
ICNC1
R/W
0
6
ICES1
R/W
0
5
ICPE
0
R/W
4
-
R
0
page 107
3
CTC1
R/W
0
for a detailed description.
2
CS12
R/W
0
1
CS11
0
R/W
0
CS10
R/W
0
1138I–FPSLI–1/08
TCCR1B