ATmega8(L)
Alternate Functions of Port C The Port C pins with alternate functions are shown in Table 25.
Table 25. Port C Pins Alternate Functions
Port Pin
Alternate Function
PC6
RESET (Reset pin)
ADC5 (ADC Input Channel 5)
SCL (Two-wire Serial Bus Clock Line)
PC5
PC4
ADC4 (ADC Input Channel 4)
SDA (Two-wire Serial Bus Data Input/Output Line)
PC3
PC2
PC1
PC0
ADC3 (ADC Input Channel 3)
ADC2 (ADC Input Channel 2)
ADC1 (ADC Input Channel 1)
ADC0 (ADC Input Channel 0)
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
59
2486M–AVR–12/03
ATMEL [ ATMEL ]
