Rainbow Electronics ATmega103L - Manual (Page 88)

ATmega603/103
88
Port E as general digital I/O
PEn, General I/O pin: The DDEn bit in the DDRE register selects the direction of this pin. If DDEn is set (one), PEn is con-
figured as an output pin. If DDEn is cleared (zero), PEn is configured as an input pin. If PEn is set (one) when configured as
an input pin, the MOS pull up resistor is activated. To switch the pull up resistor off the PEn has to be cleared (zero) or the
pin has to be configured as an output pin.The port pins are tri-stated when a reset condition becomes active, even if the
clock is not running.
Note: n: 7,6...0, pin number
Alternate Functions OF Port E
PDI/RXD - Port E, Bit 0
PDI, Serial Programming Data Input. During Serial Program Downloading, this pin is used as data input line for the
ATmega603/103.
RXD, UART Receive Pin. Receive Data (Data input pin for the UART). When the UART receiver is enabled this pin is con-
figured as an input regardless of the value of DDRD0. When the UART forces this pin to be an input, a logical one in
PORTD0 will turn on the internal pull-up.
PDO/TXD - Port E, Bit 1
PDO, Serial Programming Data Output. During Serial Program Downloading, this pin is used as data output line for the
ATmega603/103.
TXD, UART Transmit Pin.
AC+ - Port E, Bit 2
AC+ - Analog Comparator Positive Input. This pin is directly connected to the positive input of the analog comparator.
AC- - Port E, Bit 3
AC- - Analog Comparator Negative Input. This pin is directly connected to the negative input of the analog comparator.
INT4 .. INT7 - Port E, Bit 4-7
INT4 .. INT7 - External Interrupt sources 4 - 7: The PE4 - PE7 pins can serve as external interrupt sources to the MCU.
Interrupts can be triggered by low level or positive or negative edge on these pins. The internal pull up MOS resistors can
be activated as described above. See the interrupt description for further details, and how to enable the sources.
Port E Schematics
Note that all port pins are synchronized. The synchronization latches are however, not shown in the figures.
Table 35. DDEn Bits on Port E Pins
DDEn PORTEn I/O Pull up Comment
0 0 Input No Tri-state (Hi-Z)
0 1 Input Yes PDn will source current if ext. pulled low.
1 0 Output No Push-Pull Zero Output
1 1 Output No Push-Pull One Output