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ZEUS Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue D 60
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).
10K
+5V
P(0-15)
PXA270 MAX7313
I2C
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.