Embedded EEPROM Specification - picmg

4 EEPROM Header Components.
4.1 Concepts
There are multiple goals for an EEPROM header. One of the primary goals is to provide a mechanism
for content Identification. This goal is achieved through inclusion of a header Id. A Secondary Goal is
to provide information at fixed offsets. The purpose of providing information at fixed offsets is to allow
for easier access. One of the costs of storing dynamic information in an EEPROM is that at an early
system state it may not be convenient or possible to parse complex structures or hierarchies in order
to extract information. To this extend it is advisable to segregate the information we wish to store in
EEPROMs into 2 categories. Low Cost Access Information and Normal Cost Access Information. The
Low Cost Access Information may be stored in the EEPROM Header. To Prevent Contention Header
space is allocated in the following order.
1. EeeP Specific Header components.
2. Platform Specific Header Additions.
3. Vendor Specific Header Additions.
4.2 Common EeeP EEPROM Header
typedef struct EeePCmn_s{
uint8_t DontCareByte;/* 0x00 Don't Care Byte
* The purpose of this
* Byte is to reduce the Damage
* Extended Index read access is
* used on a Standard Index Device
*
*/
uint8_t EepId[2] ; /* 0x01 3P */
# define EEEP_EEPROM_MARKER "3P"
uint8_t SpecRev ; /* 0x03 EeeP Specification Revision
*/
uint8_t
uint8_t
}EeePCmn_t;
EEP_HDR_C_STRUCT 1: Common EEPROM Header
4.2.1 Description
Standardized Header Entry point to allow for standardized Cross platform, Cross Vendor identification
and access.
4.2.2 Header Elements
BlkOffset ; /* 0x04 Absolute Offset to
* First Dynamic Block
* in words(2 bytes)
*/
DeviceDesc ; /* 0x05 Device Descriptor
*/
4.2.2.1 Dont Care Byte(DontCareByte)
The purpose of this Byte is to reduce the the damage, if the incorrect access method is used on a
standard EEPROM. I.E. extended Index read access is used to read from a Standard Index
Device. In this scenario the second Command/Index byte is interpreted as a Data byte and is
written to the MSB Index.
4.2.2.2 EEPROM ID(EepId)
EEPROM Identifier. Defined as ASCII “3P”. To allow for EEPROM Identification.
PICMG® EEEP R1.0 Embedded EEPROM Specification, August 8, 2010 page 18 of 84