Intermec Sabre 1555 Programmer's Reference Manual page 40

Sabre 1555 RFID & Bar Code Reader Programmer's Reference Manual
Tag Memory Architecture
The ASIC provides 128 bytes of memory, addresses 0-127. The first 12 bytes are
factory programmed including an 8-byte unique identification code in address
locations 0 through 7 and permanently locked. Future releases of the 1555 product
will have the Privileges function enabled, which will occupy locations 12 through 14.
The remaining memory can be programmed with customer-specific information. If
data is stored in ASCII format, and no other compression technique is employed, then
1 byte of memory will store roughly one alpha-numeric character. Storing in
hexadecimal format allows for a greater number of values to be stored since each
hexadecimal code can be stored in a single byte. In the majority of applications, most
of the data in the reserved locations (including the unique 8-byte Tag ID) is stored in
hexadecimal format - as represented with a 2-character nibble per byte. Each byte
stored on the ASIC is assigned a location corresponding to the order of the data to be
transmitted (locations 0 to 127). These location assignments are used to set up some
of the special functions available with the Sabre 1555.
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