User manual

Detailed hardware description
Issue E 53
I²C bus
The PXA270 I²C interface is brought out to the COMs connector J19. See the section
J19 – Serial ports – COM3/4
, page 80, for connection details.
I²C bus is also used with the Quick Capture interface. See the section Quick Capture
camera interface
, page 54.
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.