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ZEUS Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue D 29
On-Board GPIO expanders pin assignments
Two GPIO expanders (MAX7313) are used to provide additional GPIOs for use with
different on-board peripherals. The GPIO expanders are connected to the I
2
C bus of
PXA270 and are accessible through I
2
C bus addresses 0x21 and 0x22.
The following tables summarize the use of the 17 GPIO pins of MAX7313 on ZEUS
board, and indicate their direction and active level.
Expander 1 - I2C Address 0x21
GPIO Signal name Dir Active Function
Power-up
state
See section…
0 U3_RS232EN Output High UART3 RS232 enable PU
1 U3_RS422EN Output High UART3 RS422 enable PU
2 U3_TERM# Output Low
UART3 termination
enable
PU
COM3 –
RS232/RS485/RS422
interface
, page 54
3 USER_LED1# Output Low User LED 1 PU
4 USER_LED2#
Output
Low User LED 2 PU
5 USER_LED3# Output Low User LED 3 PU
User LEDs
, page 96
6 USER_LINK3 Input NA User jumper 3 Jumper
JP1 – User jumpers
, page 9
3
7 NOT USED PU
8 GSM_ON Output
See note
1 below
Modem enable OD
9 GSM_STS Input High Modem ON/OFF status Low
10 GPS_ON Output High GPS module enable PU
11 GPS_PSUON Input NA Not Used PU
12 GPS_BOOT Input NA Not Used OD
13 GPS_PPS Input NA GPS Pulse Per Second -
Wireless modem and GPS
receiver
, page 35
14 USER_LINK4 Input NA User jumper 4 Jumper
JP1 – User jumpers
,
page 93
15 U4_RS485EN Output High UART4 RS485 enable PU
16 U4_TERM# Output Low
UART4 termination
enable
PU
COM4 – RS422/485
interface
, page 55
Key:
Dir - Pin direction Active - Function active level or edge
PU - On-board 10K pull-up OD - Open Drain
Note 1: Please see the datasheet of the particular module used.