AMI Analyzer Manual
Communications
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45
Holding registers can be written to unless they have an N in the Writeable column above. Coil 24 must be
set for this to be enabled. Please be extremely careful about setting any of these registers. If you get it
wrong the analyzer may behave in unpredictable ways.
If you write into more than one register at once, using command 16, but there is an error – perhaps you
attempt to write into a non-writable one, or use a value outside the acceptable range - the procedure will
stop at that register and return an error message. It will place in register 22 the address of the register that
failed. This means that the command succeeded in all prior register writes. It will not attempt to continue
past the failed write. Any further error will overwrite this register (22) with the latest error.
Higher Registers:
The registers above 42 report the various logging features of the analyzer. These are reported as ASCII
characters packed 2-to-a-word in contiguous registers from 43 upwards to 253. The final entry in each set is
a zero (0x00) in a word – the only time 0x00 will appear since all the other characters are ASCII. If the length
of the entry is shorter than the maximum allowed, the rest of the entry (after the zero) might be random
gibberish and should be ignored.
The span history is located in registers 44 through 54, then 55 through 65, then 66 through 76, then 77
through 87, and then 88 through 98.
The span history is structured as dd:mm:yy-XXX-YYYppm, with the number of X’s and Y’s varying. XXX is the
span factor after the span, and YYY is the span gas used as read by the analyzer – for example, if the analyzer
is spanned to 80.0ppm gas, this value will be 80.0ppm. If it was spanned on air, to 20.90%, this value would
be 20.9%. A total of five such sets of data are stored, the most recent being the first set. Month and day are
stored as either single or double digits, so make sure you delimit the values with the colons and dashes.
The start up history continues above that, but as this contains an odd number of characters words are shared
between two adjacent entries. This is structured as hh:dd:mm:yy-XX again with either single or double digits
for the hh, dd, and mm entries. The XX gives the number of memory errors encountered during the start up
(the analyzer stores critical values four separate times, and takes a majority vote if any of them don’t match
the others).
Ten sets are stored, the most recent being first.
Above register 175 can be found the Low Power entries, occupying ten registers each.
These report the times that low power (below 8.5V) was detected, and when normal power was restored
(above 10V). These records are structured Lo:hh:dd:mm:yy, and OK:hh:dd:mm:yy respectively. A total of
ten records are stored, usually five of each.
In every case, nonsense values may be present if the unit hasn’t had that number of experiences. If so the
colons won’t be present in the strings.
None of these higher registers may be written into.
