DANIEL 2234 Manual page 112

__________________________ MODEL 2234 DIGITAL FLOW COMPUTER
The Model 2234 performs diagnostic checks on both the RAM and the
PROM memories to insure the reliability of the calculations performed and
the safe storage of the resulting data. If a memory failure occurs, the system
halts all flow calculations because their reliability would be uncertain. A
diagnostic message is displayed on the front panel in the form MEM XX00
where XX is the starting address of the memory IC chip which has failed.
Table 3-4 shows the relation of the address displayed to actual IC chips.
The RAM memory diagnostic check is run during the initialize sequence,
after the operator has simultaneously pressed both the CMD and CLR keys
to clear all memory and start a configuration (CNFIG) prompting sequence.
The PROM memory diagnostic check is run every ten seconds during normal
use of the computer.
The diagnostic test runs successfully even if all RAM memory fails and
nearly all PROM memory fails. All that is required is that the small section
of PROM memory containing the diagnostic routines be operable. If this
portion of memory fails, the system "watchdogs" (causing the indicator lights
on the front panel to blink) halts further processing.
Even though the system ceases to calculate rates and totals upon detecting
a memory failure, the diagnostic test continues to run. If the memory checks
out good on the next pass, the system is allowed to resume processing as if
a temporary power failure has occurred.
In the event of PROM memory failure, all measurement data is maintained
in RAM memory. To access this information, correct the PROM memory
problem by replacing the defective chip.
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SECTION 3