AT90S/LS4434 and AT90S/LS8535
34
Figure 32.
ICP Pin Schematic Diagram
If the Noise Canceler function is enabled, the actual trigger condition for the capture event is monitored over four samples
and all four must be equal to activate the capture flag. The input pin signal is sampled at XTAL clock frequency.
Timer/Counter1 Control Register A – TCCR1A
•
Bits 7, 6 – COM1A1, COM1A0: Compare Output Mode1A, Bits 1 and 0
The COM1A1 and COM1A0 control bits determine any output pin action following a compare match in Timer/Counter1.
Any output pin actions affect pin OC1A (Output CompareA pin 1). This is an alternative function to an I/O port and the cor-
responding direction control bit must be set (one) to control an output pin. The control configuration is shown in Table 12.
•
Bits 5, 4 – COM1B1, COM1B0: Compare Output Mode1B, Bits 1 and 0
The COM1B1 and COM1B0 control bits determine any output pin action following a compare match in Timer/Counter1.
Any output pin actions affect pin OC1B (Output CompareB). This is an alternative function to an I/O port and the corre-
sponding direction control bit must be set (one) to control an output pin. The control configuration is given in Table 12.
Note:
X = A or B.
In PWM mode, these bits have a different function. Refer to Table 16 for a detailed description. When changing the
COM1X1/COM1X0 bits, Output Compare Interrupt 1 must be disabled by clearing their Interrupt Enable bits in the TIMSK
Register. Otherwise an interrupt can occur when the bits are changed.
•
Bits 3..2 – Res: Reserved Bits
These bits are reserved bits in the AT90S4434/8535 and always read zero.
•
Bits 1..0 – PWM11, PWM10: Pulse Width Modulator Select Bits
These bits select PWM operation of Timer/Counter1 as specified in Table 13. This mode is described on page 38.
Bit
7
6
5
4
3
2
1
0
$2F ($4F)
COM1A1
COM1A0
COM1B1
COM1B0
–
–
PWM11
PWM10
TCCR1A
Read/Write
R/W
R/W
R/W
R/W
R
R
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
Table 12.
Compare 1 Mode Select
COM1X1
COM1X0
Description
0
0
Timer/Counter1 disconnected from output pin OC1X
0
1
Toggle the OC1X output line.
1
0
Clear the OC1X output line (to zero).
1
1
Set the OC1X output line (to one).