Chapter 8: EEPROM Specifications
Overview
Psion Teklogix Omnii HDK User Manual
117
8.1
Overview
This chapter describes and defines the content of the EEPROMs that are used to identify modules
attached to Omnii.
8.2
EEPROM Hardware
Theory of Operation
Expansion modules should be equipped with a Maxim DS2431 1-wire EEPROM to identify the
module and its properties to the system. This information is displayed to the user in the System
Properties Control Panel applet, and is used to load appropriate software drivers.
The required pull-ups for the operation of this EEPROM are included on the main logic board.
Due to the slow transfer speed of the EEPROMs, it is not recommended to use larger EEPROMs,
or to store larger amounts of information in them. Also, since the EEPROM data is read from the
SysCon (system controller), it is not recommended to use the EEPROM storage for any
operational functions beyond initial device setup at boot time. Accessing the EEPROM memory
during device operation will consume the SysCon processing time and may slow the system
down.
8.3
EEPROM Data Specification
The module EEPROM is used to identify the hardware and load appropriate software drivers. The
identity will be displayed to the user in the System Properties panel of the System control panel,
and will be accessible to drivers and applications.
This section describes the fields of the EEPROM which are predefined for this purpose.
Manufacturers are free to use unused areas of the EEPROM for their own configuration purposes.
All modules will share the common EEPROM fields below, and each module type may have
specific additional fields.
8.3.1
Common EEPROM Fields
Unused fields/bytes have the value 0xFF. If the specified fields are set to 0xFF, "Unknown" is
displayed in the corresponding entry in the System Properties Control Panel.
Data in a text field must start at the first byte of the field. If the data does not fill the text field, the
first occurrence of byte 0xFF or 0x00 terminates the text string.
Note: The expansion module one-wire EEPROM may not be writable at all times during device
operation and therefore should not be relied on for use after boot time.
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