AT697F datasheet(50/155 Pages) ATMEL

50 / 155 page

7703C–AERO–6/09

AT697F ADVANCE INFORMATION

configuring the pin

The upper 16 bits of the general purpose interface can only be configured as outputs or inputs

on byte basis. D[15:8] is referenced as the medium byte when D[7:0] is referenced as the lower

byte.

Each byte from D[15:0] consists of two register fields. As shown in the “Register Description”

section, the direction fields are accessed at IODIR address when data fields at IODAT address.

The IODIR MEDDIR bit and the IODIR LOWDIR bit select the direction for respectively the

medium byte ( D[15:8] ) and the lower byte ( D[7:0] ). If MEDDIR (or LOWDIR) is written logic

one, the corresponding byte in D[15:0] is configured as output. If written logic zero, the byte is

configured as an input.

When configured as an input, a read of the IODAT MEDDAT fileds returns the current value of

D[15:8]. When configured as an output, the logical value from IODAT MEDDAT field is trans-

lated in physical values on D[15:8] bus.

When configured as an input, a read of the IODAT LOWDAT fileds returns the current value of

D[7:0]. When configured as an output, the logical value from IODAT LOWDAT field is trans-

lated in physical values on D[7:0] bus.

switching between input

& output

When the medium byte (or the lower) is switched from input to output by switching MEDDIR (or

LOWDIR), the value of MEDDAT (or LOWDAT) is immediatly driven on the corresponding pin.

When switched from output to input by toggling MEDDIR (or LOWDIR), the value from the pins

are immediatly written to MEDDAT (or LOWDAT).

GPI Alternate

functions

Most GPI pins have alternate functions in addition to being general I/O. Facilities like serial com-

munication link, interrupt input and configuration are made available through these functions.

The following table summaryses the assignement of the alternate functions.

Table 19.

GPI port pin

Alternate function

PIO[15]

TXD1 - UART1 transmitter data

PIO[14]

RXD1 - UART1 receiver data

PIO[13]

RTS1 - UART1 request-to-send

PIO[12]

CTS1 - UART1 clear-to-send

PIO[11]

TXD2 - UART2 transmitter data

PIO[10]

RXD2 - UART2 receiver data

PIO[9]

RTS2 - UART2 request-to-send

PIO[8]

CTS2 - UART2 clear-to-send

PIO[3]

UART clock - Use as alternative UART clock

PIO[2]

EDAC enable - Enable EDAC checking at reset

PIO[1:0]

Prom width - Defines PROM bus width at reset

GPI alternate functions

In addition to these alternate functions, each GPI interface pin can be configured as an interrupt

input to catch interrupt from external devices. Up to four interrupts can be configured on the GPI

interface by programming the I/O interrupt register (IOIT).

For a detailed description of the external interrupt configuration, please refer to the “Traps and

Interrupts” section.

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