Datasheet

SDA, Two-wire Serial Interface Data: When the TWEN bit in TWCR is set (one) to enable the Two-wire
Serial Interface, pin PC1 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. When this pin is
used by the Two-wire Serial Interface, the pull-up can still be controlled by the PORTC1 bit.
• SCL – Port C, Bit 0
SCL, Two-wire Serial Interface Clock: When the TWEN bit in TWCR is set (one) to enable the Two-wire
Serial Interface, pin PC0 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. When this pin is
used by the Two-wire Serial Interface, the pull-up can still be controlled by the PORTC0 bit.
The tables below relate the alternate functions of Port C to the overriding signals shown in Alternate Port
Functions.
Table 17-10. Overriding Signals for Alternate Functions in PC7:PC4
Signal
Name
PC7/TOSC2 PC6/TOSC1 PC5/TDI PC4/TDO
PUOE AS2 AS2 JTAGEN JTAGEN
PUOV 0 0 1 0
DDOE AS2 AS2 JTAGEN JTAGEN
DDOV 0 0 0 SHIFT_IR +
SHIFT_DR
PVOE 0 0 0 JTAGEN
PVOV 0 0 0 TDO
DIEOE AS2 AS2 JTAGEN JTAGEN
DIEOV 0 0 0 0
DI – – – –
AIO T/C2 OSC OUTPUT T/C2 OSC INPUT TDI –
Table 17-11. Overriding Signals for Alternate Functions in PC3:PC0
(1)
Signal
Name
PC3/TMS PC2/TCK PC1/SDA PC0/SCL
PUOE JTAGEN JTAGEN TWEN TWEN
PUOV 1 1 PORTC1 • PUD PORTC0 • PUD
DDOE JTAGEN JTAGEN TWEN TWEN
DDOV 0 0 SDA_OUT SCL_OUT
PVOE 0 0 TWEN TWEN
PVOV 0 0 0 0
DIEOE JTAGEN JTAGEN 0 0
Atmel ATmega32A [DATASHEET]
Atmel-8155I-ATmega32A_Datasheet_Complete-08/2016
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