Serial Port Communications
Operator’s Manual 3
–13
A “short integer” value is contained in one register whereas a “long integer” or
“floating point” value requires two contiguous registers. The registers are
defined as Read or Read/Write.
An appropriate password must be downloaded to the password register prior
to writing to most registers. The User Level 1 (L1) user password 3142 will
allow access to those registers which have been pre-defined as user
configurable. Other writable registers can only be downloaded or changed by
SpectraSensors support personnel using a User Level 2 (L2) password.
Endianness
Endianness, often referred to as byte order, is the ordering of individually
addressable sub-units (words, bytes, or even bits) within a longer data word.
Byte orders with the most versus least significant byte first are called big-
endian and little-endian, respectively. In SpectraSensors analyzers, all bytes
are stored big-endian. Thus, for floating point and long-integer data types, the
byte order will look like:
ToenableModbuscommunications
1. Confirm that the serial cable has been properly connected.
2. Power up the analyzer (see “Powering Up the Analyzer” on page
2-1).
3. Enter Mode 2 by pressing the # key followed by the 2 key.
The LCD prompts for a numeric password. Enter the user password
(3142) on the keypad, then press the * key to enter the number to
enter Mode 2 (Set Parameter Mode).
Use caution when writing to registers as changing the value of a
writable register may affect the calibration of the analyzer.
HighWord-HighByte HighWord-LowByte LowWord-HighByte LowWord-LowByte
The generic serial output (HyperTerminal) is disabled if either
Gould or Daniel Modbus is selected.
<SET PARAMETER MODE>
Enter password
NS 5.14-XXXX
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