Rainbow-electronics AT90S2313 Manual do Utilizador descarregar pdf (Página 29)

AT90S2313

0839I–AVR–06/02

Timer/Counter0 Control

• Bits 7..3 – Res: Reserved Bits

These bits are reserved bits in the AT90S2313 and always read zero.

• Bits 2,1,0 – CS02, CS01, CS00: Clock Select0, Bit 2,1 and 0

The Clock Select0 bits 2, 1, and 0 define the prescaling source of Timer/Counter0.

The Stop condition provides a Timer Enable/Disable function. The CK down divided

modes are scaled directly from the CK Oscillator clock. If the external pin modes are

used for Timer/Counter0, transitions on PD4/(T0) will clock the counter even if the pin is

configured as an output. This feature can give the user software control of the counting.

Timer/Counter0 – TCNT0

The Timer/Counter0 is realized as an up-counter with read and write access. If the

Timer/Counter0 is written and a clock source is present, the Timer/Counter0 continues

counting in the timer clock cycle following the write operation.

Bit 7 6 5 4 3 2 1 0

$33 ($53) –– – – –CS02 CS01 CS00 TCCR0

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

Initial value 0 0 0 0 0 0 0 0

Table 7. Clock 0 Prescale Select

CS02 CS01 CS00 Description

0 0 0 Stop, the Timer/Counter0 is stopped.

001CK

010CK/8

011CK/64

100CK/256

1 0 1 CK/1024

1 1 0 External Pin T0, falling edge

1 1 1 External Pin T0, rising edge

Bit 76543210

$32 ($52) MSB LSB TCNT0

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

Initialvalue00000000

1 2 ... 24 25 26 27 28 29 30 31 32 33 34 ... 91 92

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