58
AT90S2313
0839G–08/01
Port D Data Register – PORTD
Port D Data Direction Register
– DDRD
Port D Input Pins Address –
PIND
The Port D Input Pins address (PIND) is not a register; this address enables access to
the physical value on each Port D pin. When reading PORTD, the Port D Data Latch is
read, and when reading PIND, the logical values present on the pins are read.
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 configured 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.
Note: 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.
Bit 76543210
$12 ($32)
– PORTD6 PORTD5 PORTD4 PORTD3 PORTD2 PORTD1 PORTD0 PORTD
Read/Write R R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 76543210
$11 ($31) – DDD6 DDD5 DDD4 DDD3 DDD2 DDD1 DDD0 DDRD
Read/Write R R/W R/W R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 76543210
$10 ($30) – PIND6 PIND5 PIND4 PIND3 PIND2 PIND1 PIND0 PIND
Read/WriteRRRRRRRR
Initial value 0 N/A N/A N/A N/A N/A N/A N/A
Table 20. DDDn Bits on Port D Pins
DDDn PORTDn I/O Pull-up Comment
0 0 Input No Tri-state (High-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
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