Manual

AT90S/LS8535

1041H–11/01

Note: X = A or B.

In PWM mode, these bits have a different function. Refer to Table 15 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. Other-

wise an interrupt can occur when the bits are changed.

• Bits 3..2 – Res: Reserved Bits

These bits are reserved bits in the AT90S8535 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 12. This mode

is described on page 40.

Timer/Counter1 Control

• Bit 7 – ICNC1: Input Capture1 Noise Canceler (4 CKs)

When the ICNC1 bit is cleared (zero), the Input Capture Trigger Noise Canceler function

is disabled. The input capture is triggered at the first rising/falling edge sampled on the

ICP (input capture pin) as specified. When the ICNC1 bit is set (one), four successive

samples are measured on the 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 (ICP). While

the ICES1 bit is set (one), the Timer/Counter1 contents are transferred to the Input Cap-

ture Register (ICR1) on the rising edge of the input capture pin (ICP).

• Bits 5, 4 – Res: Reserved Bits

These bits are reserved bits in the AT90S8535 and always read zero.

Table 11. 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).

Table 12. PWM Mode Select

PWM11 PWM10 Description

0 0 PWM operation of Timer/Counter1 is disabled

0 1 Timer/Counter1 is an 8-bit PWM

1 0 Timer/Counter1 is a 9-bit PWM

1 1 Timer/Counter1 is a 10-bit PWM

Bit 7654 3210

$2E ($4E) ICNC1 ICES1 ––CTC1 CS12 CS11 CS10 TCCR1B

Read/Write R/W R/W R R R/W R/W R/W R/W

Initial Value0000 0000