Port c data direction register – ddrc, Port c input pins address – pinc, Port c as general digital i/o – Rainbow Electronics AT90S8515 User Manual
Page 71: Table 22. ddcn effects on port c pins
71
AT90S8515
0841G–09/01
Port C Data Direction Register
– DDRC
Port C Input Pins Address –
PINC
The Port C Input Pins address (PINC) is not a register; this address enables access to
the physical value on each Port C pin. When reading PORTC, the Port C Data Latch is
read and when reading PINC, the logical values present on the pins are read.
Port C as General Digital I/O
All eight pins in Port C have equal functionality when used as digital I/O pins.
PCn, general I/O pin: The DDCn bit in the DDRC register selects the direction of this pin.
If DDCn is set (one), PCn is configured as an output pin. If DDCn is cleared (zero), PCn
is configured as an input pin. If PORTCn is set (one) when the pin is configured as an
input pin, the MOS pull-up resistor is activated. To switch the pull-up resistor off,
PORTCn has to be cleared (zero) or the pin has to be configured as an output pin. The
Port C pins are tri-stated when a reset condition becomes active, even if the clock is not
active.
Note:
n: 7…0, pin number
Bit
7
6
5
4
3
2
1
0
$14 ($34)
DDC7
DDC6
DDC5
DDC4
DDC3
DDC2
DDC1
DDC0
DDRC
Read/Write
R/W
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
7
6
5
4
3
2
1
0
$13 ($33)
PINC7
PINC6
PINC5
PINC4
PINC3
PINC2
PINC1
PINC0
PINC
Read/Write
R
R
R
R
R
R
R
R
Initial Value
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table 22. DDCn Effects on Port C Pins
DDCn
PORTCn
I/O
Pull-up
Comment
0
0
Input
No
Tri-state (high-Z)
0
1
Input
Yes
PCn will source current if ext. pulled low.
1
0
Output
No
Push-pull Zero Output
1
1
Output
No
Push-pull One Output