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ZEUS Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue D 58
I²C bus
The PXA270 I²C interface is brought out to the COMs connector J19. See the section
J19 – Serial ports – COM3/4
, page 88, for connection details.
I²C bus is also used with the Quick Capture interface. See the section Quick Capture
camera interface
, page 59.
The following table lists the on-board I²C devices:
Device name I²C address
External General Purpose I/O 0x20
On-board GPIO Expander 1 0x21
On-board GPIO Expander 2 0x22
Temperature Sensor (LM75A) 0x48
RTC (Intersil ISL1208) 0x6F
Config EPROM 0x50-0x57
The I²C unit supports a fast mode operation of 400KB/s and a standard mode of
100KB/s.
Fast-mode devices are downward compatible and can communicate with standard-
mode devices in a 0 to 100KB/s I²C bus system. As standard-mode devices, however,
are not upward compatible, they should not be incorporated in a fast-mode I²C bus
system as they cannot follow the higher transfer rate and unpredictable states would
occur.
The I²C interface does not support the hardware general call, 10-bit addressing,
high-speed mode (3.4Mbit/s) or CBUS compatibility.
You should keep the total bus load below 200pF.