ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 73

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

14. I/O-Ports
14.1
9223B–AVR–09/11
Overview
All AVR ports have true Read-Modify-Write functionality when used as general digital I/O
ports. This means that the direction of one port pin can be changed without unintentionally
changing the direction of any other pin with the SBI and CBI instructions. The same applies
when changing drive value (if configured as output) or enabling/disabling of pull-up resistors (if
configured as input). Each output buffer has symmetrical drive characteristics with both high
sink and source capability. The pin driver is strong enough to drive LED displays directly. All
port pins have individually selectable pull-up resistors with a supply-voltage invariant resis-
tance. All I/O pins have protection diodes to both V
Refer to
Figure 14-1. I/O Pin Equivalent Schematic
All registers and bit references in this section are written in general form. A lower case “x” rep-
resents the numbering letter for the port, and a lower case “n” represents the bit number.
However, when using the register or bit defines in a program, the precise form must be used.
For example, PORTB3 for bit no. 3 in Port B, here documented generally as PORTxn. The
physical I/O Registers and bit locations are listed in
Three I/O memory address locations are allocated for each port, one each for the Data Regis-
ter – PORTx, Data Direction Register – DDRx, and the Port Input Pins – PINx. The Port Input
Pins I/O location is read only, while the Data Register and the Data Direction Register are
read/write. However, writing a logic one to a bit in the PINx Register, will result in a toggle in
the corresponding bit in the Data Register. In addition, the Pull-up Disable – PUD bit in
MCUCR disables the pull-up function for all pins in all ports when set.
Using the I/O port as General Digital I/O is described in
74. Most port pins are multiplexed with alternate functions for the peripheral features on the
device. How each alternate function interferes with the port pin is described in
Functions” on page
alternate functions.
Note that enabling the alternate function of some of the port pins does not affect the use of the
other pins in the port as general digital I/O.
Atmel ATmega48PA/88PA/168PA [Preliminary]
“Electrical Characteristics” on page 314
Pxn
79. Refer to the individual module sections for a full description of the
C
pin
for a complete list of parameters.
CC
“Register Description” on page
and Ground as indicated in
"General Digital I/O" for
“Ports as General Digital I/O” on page
See Figure
R
Details
pu
Logic
“Alternate Port
Figure
91.
14-1.
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