AT90LS8535_14 Datasheet, PDF (36/127 Pages) ATMEL Corporation – Data and Nonvolatile Program Memories

the counter on compareA match and actions on the Output Compare pins on both com-
pare matches.
Timer/Counter1 can also be used as an 8-, 9- or 10-bit Pulse Width Modulator. In this
mode the counter and the OCR1A/OCR1B registers serve as a dual glitch-free stand-
alone PWM with centered pulses. Refer to page 40 for a detailed description of this
function.
The Input Capture function of Timer/Counter1 provides a capture of the Timer/Counter1
contents to the Input Capture Register (ICR1), triggered by an external event on the
Input Capture Pin (ICP). The actual capture event settings are defined by the
Timer/Counter1 Control Register (TCCR1B). In addition, the Analog Comparator can be
set to trigger the input capture. Refer to “Analog Comparator” on page 66 for details on
this. The ICP pin logic is shown in Figure 32.
Figure 32. ICP Pin Schematic Diagram
Timer/Counter1 Control
Register A – TCCR1A
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.
Bit
7
6
5
4
3
$2F ($4F) COM1A1 COM1A0 COM1B1 COM1B0
–
Read/Write
R/W
R/W
R/W
R/W
R
Initial Value
0
0
0
0
0
2
1
0
–
PWM11 PWM10 TCCR1A
R
R/W
R/W
0
0
0
• 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 corresponding
direction control bit must be set (one) to control an output pin. The control configuration
is shown in Table 11.
• 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 corresponding direction
control bit must be set (one) to control an output pin. The control configuration is given in
Table 11.
36 AT90S/LS8535
1041H–11/01