External general purpose i/o – Eurotech Appliances ZEUS PXA270 User Manual

Page 60

ZEUS Technical Manual

Detailed hardware description

External General purpose I/O

A Maxim MAX7313 I²C I/O Expander provides sixteen general purpose input/output

lines on the header J7. Each I/O port can be individually configured as either an open-

drain current-sinking output rated at 50mA with10K pull-up to 5V, or a logic input with

transition detection. The I/O Expander inputs are 5V tolerant.

The I/O Expander is addressable at I²C serial bus address 0x20 and is accessed in

fast-mode operation at 400 kbps. On power-up all control registers are reset and the

MAX7313 enters standby mode. Power-up status makes all ports into inputs, so the

state of all 17 ports (P0-P16) is logic high (through 10K pull-up to 5V).

See the section

, for connector pinout and mating

connector details. The signals on J7 correspond to the pin names of the MAX7313

(P0-P15).

10K

+5V

P(0-15)

PXA270

MAX7313

I2C

P16

Port 16 of the MAX7313 is configured as an interrupt, so that any I/O Expander GPIO

pin configured as an input can cause the PXA270 to be interrupted on GPIO1. These

can also be used as PXA270 wake-up sources from sleep mode.