Atmel AT90S2313 - Alternate Functions of Port D

AT90S2313
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Port D as General Digital I/O
PDn, General I/O pin: The DDDn bit in the DDRD register selects the direction of this pin. If DDDn is set (one), PDn is con-
figured as an output pin. If DDDn is cleared (zero), PDn is configured as an input pin. If PORTDn is set (one) when
configured as an input pin the MOS pull up resistor is activated. To switch the pull up resistor off the PORTDn has to be
cleared (zero) or the pin has to be configured as an output pin. The Port D pins are tri-stated when a reset condition
becomes active, even if the clock is not active.
n: 6…0, pin number.
Alternate Functions of Port D
The alternate functions of Port D are:
•
ICP - Port D, Bit 6
Timer/Counter1 Input Capture pin. See the Timer/Counter1 description for further details.
•
T1 - Port D, Bit 5
T1, Timer 1 clock source. See the timer description for further details.
•
T0 - Port D, Bit 4
T0, Timer/Counter0 clock source. See the Timer description for further details.
•
INT1 - Port D, Bit 3
INT1, External Interrupt source 1. The PD3 pin can serve as an external interrupt source to the MCU. See the interrupt
description for further details, and how to enable the source.
•
INT0 - Port D, Bit 2
INT0, External Interrupt source 0. The PD2 pin can serve as an external interrupt source to the MCU. See the interrupt
description for further details, and how to enable the source.
•
TXD - Port D, Bit 1
Transmit Data (Data output pin for the UART). When the UART transmitter is enabled, this pin is configured as an output
regardless of the value of DDRD1.
•
RXD - Port D, Bit 0
Receive Data (Data input pin for the UART). When the UART receiver is enabled this pin is configured as an input regard-
less 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.
Table 20. DDDn Bits on Port D Pins
DDDn PORTDn 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