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ATmega8A [DATASHEET]
8159E–AVR–02/2013
13.3.3
Alternate Functions of Port C
The Port C pins with alternate functions are shown in
Table 13-5.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 unpro-
grammed, 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 Inter-
face. 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 digital 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 Inter-
face, 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 digital 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
PC1 can also be used as ADC input Channel 1. Note that ADC input channel 1 uses analog power.
Table 13-5.
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)