AT&T 3B2/300 Technical Reference Manual page 378

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Nonvolatile Random Access Memory
The Nonvolatile Random Access Memory (NVRAM) is a single chip providing 2K by 8 bits of
memory for the storage of system configuration parameters. The chip is an 8K by 8 bit chip, but only
2K of the chip is used. Only 512 bytes of the 2K used is actually allocated. Parameters include console
terminal settings, system error log, and the firmware password. NVRAM is maintained by a backup
battery in the absence of VCC. When power is removed from the system, NVRAM enable (chip select)
is inhibited to prevent an accidental write operation from destroying the NVRAM data. NVRAM
should be read and written on full word boundaries using data bus bits 07-00. The following table
further defines the contents of NVRAM.
FUNCTIONAL DESCRIPTION 3-125