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 J7 – GPIO connector, page 81, for connector pinout and mating connector details. The signals on J7 correspond to the pin names of the MAX7313 (P0-P15).

+5V

I2C

10K

PXA270

 

MAX7313

 

P(0-15) J7

 

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.

© 2007 Eurotech Ltd Issue D

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