AT90S1200 ATMEL Corporation, AT90S1200 Datasheet - Page 34

• Manufacturer Part Number: AT90S1200
• Description: 8-Bit Microcontroller with 1K bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Port D
Port D Data Register – PORTD
Port D Data Direction Register
– DDRD
Port D Input Pins Address –
PIND
Port D as General Digital I/O
34
AT90S1200
Three I/O memory address locations are allocated for Port D, one each for the Data
Register – PORTD ($12), Data Direction Register – DDRD ($11), and the Port D Input
Pins – PIND ($10). The Port D Input Pins address is read-only, while the Data Register
and the Data Direction Register are read/write.
Port D has seven bi-directional I/O pins with internal pull-up resistors, PD6..PD0. 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 10.
Table 10. Port D Pin Alternate Functions
The Port D Input Pins address (PIND) is not a register, and 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.
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 DDDn is configured as
an input pin, the MOS pull-up resistor is activated. To switch the pull-up resistor off, the
PORTDn bit 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.
Bit
$12
Read/Write
Initial Value
Bit
$11
Read/Write
Initial Value
Bit
$10
Read/Write
Initial Value
Port Pin
PD2
PD4
R
R
R
7
–
0
7
–
0
7
–
0
PORTD6
PIND6
DDD6
Alternate Function
INT0 (External Interrupt 0 input)
T0 (Timer/Counter 0 external input)
R/W
R/W
N/A
R
6
0
6
6
0
PORTD5
PIND5
DDD5
R/W
R/W
N/A
R
5
0
5
5
0
PORTD4
PIND4
DDD4
R/W
R/W
N/A
R
4
0
4
4
0
PORTD3
PIND3
DDD3
R/W
R/W
N/A
R
3
0
3
3
0
PORTD2
PIND2
DDD2
R/W
N/A
R/W
R
2
0
2
2
0
PORTD1
PIND1
DDD1
R/W
N/A
R/W
R
1
0
1
1
0
PORTD0
PIND0
DDD0
R/W
N/A
R/W
0838H–AVR–03/02
R
0
0
0
0
0
PORTD
DDRD
PIND