AT&T 3B2 Off-Line Diagnostic Manual page 619

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Phase Descriptions
Phase #5 - ROM Check Sum
Tes'~
Phase Name:
Type:
Function:
Test:
Time:
Warnings:
Notes:
Phase #5 Test
Network Access Unit ROM (rom)
Demand
This phase verifies the integrity of the Network Access Unit ROM.
This phase calculates a ROM check sum and compares it to the check sum
stored in ROM when the ROM was initially programmed.
1 second
None
Every Network Access Unit Erasable Programmable Read Only Memory
(EPROM) set is initially loaded with the same data. This load contains all but
6 bytes of the data required to complete a Network Access Unit EPROM load.
The six omitted bytes are those that contain the individual Network Access
Unit address. Because the address of each Network Access Unit is unique, the
data that is written into these six registers later is different for each Network
Access Unit. A check sum is generated over the unchanging data and written
into each Network Access Unit EPROM set. When generating this check sum,
the generator finds the hexadecimal value FF in each of the three unwritten
registers (OxFF is the value found in unprogrammed EPROM registers).
Prior to insertion in a Network Access Unit, each Network Access Unit EPROM
set is loaded with the 6 address bytes that differentiate that Network Access
Unit from all others.
To generate the same check sum as contained in the Network Access Unit
EPROM, the diagnostics substitute OxFF for the actual data contained in the six
Network Access Unit Address registers.
Test Number: 1
Function: This test verifies the integrity of the Network Access Unit ROM.
Procedure: Calculate a check sum over the Network Access Unit ROM and compare the
calculated check sum with the check sum stored in ROM when it was initially
programmed.
Hardware Tested: The Network Access Unit ROM is tested.
Data Returned The failed test number, the expected check sum value, and the actual check
sum value are returned.
STAR LAN INTERFACE DIAGNOSTICS 15-7