AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 63

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

Ports as General Digital
I/O
Configuring the Pin
4250C–CAN–03/04
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 30 shows a
functional description of one I/O-port pin, here generically called Pxn.
Figure 30. General Digital I/O
Note:
Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in
“Register Description for I/O-Ports” on page 86, the DDxn bits are accessed at the
DDRx I/O address, the PORTxn bits at the PORTx I/O address, and the PINxn bits at
the PINx I/O address.
The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written
logic one, Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is config-
ured as an input pin.
If PORTxn is written logic one when the pin is configured as an input pin, the pull-up
resistor is activated. To switch the pull-up resistor off, PORTxn has to be written logic
zero or the pin has to be configured as an output pin
The port pins are tri-stated when reset condition becomes active, even if no clocks are
running.
Pxn
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port.
clk
SLEEP: SLEEP CONTROL
I/O
clk
PUD: PULLUP DISABLE
, SLEEP, and PUD are common to all ports.
I/O
: I/O CLOCK
(1)
SLEEP
SYNCHRONIZER
WDx: WRITE DDRx
RDx: READ DDRx
WRx: WRITE PORTx
RRx: READ PORTx REGISTER
RPx: READ PORTx PIN
WPx: WRITE PINx REGISTER
D
L
Q
Q
D
PINxn
Q
Q
AT90CAN128
RESET
RESET
PORTxn
Q
Q
Q
Q
DDxn
CLR
CLR
D
D
RRx
PUD
WDx
RDx
RPx
clk
1
0
I/O
WPx
WRx
63