Specifications

AT90S8515

0841G–09/01

Timer/Counter1 Control

• 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 the output pin. The con-

trol configuration is shown in Table 8.

• 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). The control configuration is given in Table 8.

Note: X = A or B

In PWM mode, these bits have a different function. Refer to Table 12 on page 40 for a

detailed description.

• Bits 3..2 – Res: Reserved Bits

These bits are reserved bits in the AT90S8515 and always read zero.

• Bits 1..0 – PWM11, PWM10: Pulse Width Modulator Select Bits 1 and 0

These bits select PWM operation of Timer/Counter1 as specified in Table 9. This mode

is described on page 40.

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 8. 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 9. 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