Rainbow Electronics ATmega64L - Manual (Page 58)

58
ATmega16(L)
2466B–09/01
Alternate Functions of Port C The Port C pins with alternate functions are shown in Table 28. If the JTAG interface is
enabled, the pull-up resistors on pins PC5(TDI), PC3(TMS) and PC2(TCK) will be acti-
vated even if a reset occurs.
The alternate pin configuration is as follows:
• TOSC2 - Port C, Bit 7
TOSC2, Timer Oscillator pin 2: When the AS2 bit in ASSR is set (one) to enable asyn-
chronous clocking of Timer/Counter2, pin PC7 is disconnected from the port, and
becomes the inverting output of the oscillator amplifier. In this mode, a crystal oscillator
is connected to this pin, and the pin can not be used as an I/O pin.
• TOSC1 - Port C, Bit 6
TOSC1, Timer Oscillator pin 1: When the AS2 bit in ASSR is set (one) to enable asyn-
chronous clocking of Timer/Counter2, pin PC6 is disconnected from the port, and
becomes the input of the inverting oscillator amplifier. In this mode, a crystal oscillator is
connected to this pin, and the pin can not be used as an I/O pin.
• TDI - Port C, Bit 5
TDI, JTAG Test Data In: Serial input data to be shifted in to the Instruction Register or
Data Register (scan chains). When the JTAG interface is enabled, this pin can not be
used as an I/O pin.
• TDO - Port C, Bit 4
TDO, JTAG Test Data Out: Serial output data from Instruction register or Data Register.
When the JTAG interface is enabled, this pin can not be used as an I/O pin.
• TMS - Port C, Bit 3
TMS, JTAG Test Mode Select: This pin is used for navigating through the TAP-controller
state machine. When the JTAG interface is enabled, this pin can not be used as an I/O
pin.
• TCK - Port C, Bit 2
TCK, JTAG Test Clock: JTAG operation is synchronous to TCK. When the JTAG inter-
face is enabled, this pin can not be used as an I/O pin.
• SDA - Port C, Bit 1
SDA, 2-wire Serial Interface Data: When the TWEN bit in TWCR is set (one) to enable
the 2-wire Serial Interface, pin PC1 is disconnected from the port and becomes the
Serial Data I/O pin for the 2-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
Table 28. Port C Pins Alternate Functions
Port Pin Alternate Function
PC7 TOSC2 (Timer Oscillator Pin 2)
PC6 TOSC1 (Timer Oscillator Pin 1)
PC5 TDI (JTAG Test Data In)
PC4 TDO (JTAG Test Data Out)
PC3 TMS (JTAG Test Mode Select)
PC2 TCK (JTAG Test Clock)
PC1 SDA (2-wire Serial Bus Data Input/Output Line)
PC0 SCL (2-wire Serial Bus Clock Line)