ATMEGA8 datasheet(59/303 Pages) ATMEL

59 / 303 page

ATmega8(L)

2486M–AVR–12/03

Alternate Functions of Port C

The Port C pins with alternate functions are shown in Table 25.

The alternate pin configuration is as follows:

• RESET – Port C, Bit 6

RESET, Reset pin: When the RSTDISBL Fuse is programmed, this pin functions as a

normal I/O pin, and the part will have to rely on Power-on Reset and Brown-out Reset as

its reset sources. When the RSTDISBL Fuse is unprogrammed, the reset circuitry is

connected to the pin, and the pin can not be used as an I/O pin.

If PC6 is used as a reset pin, DDC6, PORTC6 and PINC6 will all read 0.

• SCL/ADC5 – Port C, Bit 5

SCL, Two-wire Serial Interface Clock: When the TWEN bit in TWCR is set (one) to

enable the Two-wire Serial Interface, pin PC5 is disconnected from the port and

becomes the Serial Clock I/O pin for the Two-wire Serial Interface. In this mode, there is

a spike filter on the pin to suppress spikes shorter than 50 ns on the input signal, and the

pin is driven by an open drain driver with slew-rate limitation.

PC5 can also be used as ADC input Channel 5. Note that ADC input channel 5 uses dig-

ital power.

• SDA/ADC4 – Port C, Bit 4

SDA, Two-wire Serial Interface Data: When the TWEN bit in TWCR is set (one) to

enable the Two-wire Serial Interface, pin PC4 is disconnected from the port and

becomes the Serial Data I/O pin for the Two-wire Serial Interface. In this mode, there is

a spike filter on the pin to suppress spikes shorter than 50 ns on the input signal, and the

pin is driven by an open drain driver with slew-rate limitation.

PC4 can also be used as ADC input Channel 4. Note that ADC input channel 4 uses dig-

ital power.

• ADC3 – Port C, Bit 3

PC3 can also be used as ADC input Channel 3. Note that ADC input channel 3 uses

analog power.

• ADC2 – Port C, Bit 2

PC2 can also be used as ADC input Channel 2. Note that ADC input channel 2 uses

analog power.

• ADC1 – Port C, Bit 1

Table 25. Port C Pins Alternate Functions

Port Pin

Alternate Function

PC6

RESET (Reset pin)

PC5

ADC5 (ADC Input Channel 5)

SCL (Two-wire Serial Bus Clock Line)

PC4

ADC4 (ADC Input Channel 4)

SDA (Two-wire Serial Bus Data Input/Output Line)

PC3

ADC3 (ADC Input Channel 3)

PC2

ADC2 (ADC Input Channel 2)

PC1

ADC1 (ADC Input Channel 1)

PC0

ADC0 (ADC Input Channel 0)

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