AT90S/LS4434 and AT90S/LS8535
79
Figure 60.
Port C Schematic Diagram (Pins PC7)
Port D
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors.
Three I/O memory address locations are allocated for Port D, one each for the Data Register – PORTD, $12($32), Data
Direction Register – DDRD, $11($31) and the Port D Input Pins – PIND, $10($30). The Port D Input Pins address is read-
only, while the Data Register and the Data Direction Register are read/write.
The Port D output buffers can sink 20 mA. As inputs, Port D pins that are externally pulled low will source current if the
pull-up resistors are activated.
Some Port D pins have alternate functions as shown in Table 34.
Table 34.
Port D Pin Alternate Functions
Port Pin
Alternate Function
PD0
RXD (UART Input line)
PD1
TXD (UART Output line)
PD2
INT0 (External interrupt 0 input)
PD3
INT1 (External interrupt 1 input)
PD4
OC1B (Timer/Counter1 output compareB match output)
PD5
OC1A (Timer/Counter1 output compareA match output)
PD6
ICP (Timer/Counter1 input capture pin)
PD7
OC2 (Timer/Counter2 output compare match output)
