Rabbit 2000 - Access; Reading the ID Block

24 Rabbit 2000 Microprocessor
int idBlockCRC; // CRC of this block (when this
// field is set to zero)
char marker[6]; // should be 0x55 0xAA 0x55 0xAA
// 0x55 0xAA
} SysIDBlock;
6.2 Access
The BIOS will read the system ID block during startup, so all a user needs to do is access
the system ID block struct in memory. If the user desires to read the ID block off the flash,
the following function (from IDBLOCK.LIB) should be called:
int _readIDBlock(int flash_bitmap)
DESCRIPTION:
Attempts to read the system ID block from the highest flash quadrant and save it in the
system ID block structure. It performs a CRC check on the block to verify that the
block is valid. If an error occurs, SysIDBlock.tableVersion is set to zero.
PARAMETER
flash_bitmap
Bitmap of memory quadrants mapped to flash. Examples:
0x01 = quadrant 0 only
0x03 = quadrants 0 and 1
0x0C = quadrants 2 and 3
RETURN VALUE:
0 if successful
-1 if error reading from flash
2 if ID block missing
3 if ID block invalid (failed CRC check)
The WriteFlash() function does not allow writing to the ID block. Users should nor-
mally not desire to write to the ID block, but a library that contains a high-level function
that will write an ID block can be provided if a customer needs it.
If the BIOS does not find an ID block, it sets all parameters in
SysIDBlock to zero.
6.3 Reading the ID block
The following sequence of events can be used to determine if an ID block is present:
1. The top 16 bytes of the flash device are read (the first two quadrants are mapped to
flash, so 16 bytes starting at address 0x7FFF0 will be read) into a local buffer. If the
flash is smaller than 512K, it doesn’t matter because 0x7FFF0 will still represent the
start of the highest 16 bytes.