Datasheet

85
2490R–AVR–02/2013
ATmega64(L)
Alternate Functions of
Port G
In ATmega103 compatibility mode, only the alternate functions are the defaults for Port G, and
Port G cannot be used as General Digital Port Pins. The alternate pin configuration is as follows:
• TOSC1 – Port G, Bit 4
TOSC2, Timer Oscillator pin 1: When the AS0 bit in ASSR is set (one) to enable asynchronous
clocking of Timer/Counter0, pin PG4 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.
• TOSC2 – Port G, Bit 3
TOSC2, Timer Oscillator pin 2: When the AS0 bit in ASSR is set (one) to enable asynchronous
clocking of Timer/Counter0, pin PG3 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 cannot be used as an I/O pin.
• ALE – Port G, Bit 2
ALE is the external data memory Address Latch Enable signal.
•RD
– Port G, Bit 1
RD
is the external data memory read control strobe.
Table 44. Overriding Signals for Alternate Functions in PF3..PF0
Signal
Name PF3/ADC3 PF2/ADC2 PF1/ADC1 PF0/ADC0
PUOE0000
PUOV0000
DDOE0000
DDOV0000
PVOE0000
PVOV0000
DIEOE0000
DIEOV0000
DI––––
AIO ADC3 INPUT ADC2 INPUT ADC1 INPUT ADC0 INPUT
Table 45. Port G Pins Alternate Functions
Port Pin Alternate Function
PG4 TOSC1 (RTC Oscillator Timer/Counter0)
PG3 TOSC2 (RTC Oscillator Timer/Counter0)
PG2 ALE (Address Latch Enable to external memory)
PG1 RD (Read strobe to external memory)
PG0 WR
(Write strobe to external memory)