AT&T 3B2/300 Technical Reference Manual page 324

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Nonvolatile Random Access Memory
The Nonvolatile Random Access Memory (NVRAM) is a single chip providing 1024 by 4 bits
(1024 nibbles) of memory for the storage of system configuration parameters. 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
is read and written in nibbles using MOS Data Bus bits 03-00 and address bits 11-02. The following
table further defines the contents of NVRAM.
FUNCTIONAL DESCRIPTION 3-71