QUANTUM™ HD COMPRESSOR CONTROL PANEL
COMMUNICATIONS SETUP
090.040-CS (JAN 14)
Page 52
you may need to compensate.
• 7 or 8 bits selectable.
• 1 or 2 Stop bits selectable.
• Parity can be set to None, Odd or Even
• When using MODBUS® protocol (other than the
Hyperterminal example shown earlier), it is nec-
essary to use the MODBUS® Address column as
shown in the Quantum™ Data Tables. These ad-
dresses should work for most applications.
• Follow the Frick
®
specifications for data commu-
nications requirements.
• Hyperterminal can be used to test ASCII, but not
RTU or TCP/IP communications.
NOTE: Do not continuously request a setpoint change.
Communications may slow down during the process of
writing setpoints or clearing alarms. Both of these pro-
cesses involve writing to either EEPROM or Flash Memory
and does take some time. If communication requests are
being sent faster than once every couple of seconds, there
may be temporary slowdowns during these processes.
MODBUS® Data Access
Data passed to and from the Quantum™ are integer val-
ues with one decimal field assumed unless shown other-
wise or the command is sent to select two decimal fields.
For example, if the data’s value is 25.5 then the value 255
is sent. All temperatures are in degree C and all pressures
are in PSIA unless the command is sent to select the units
of the panel. A mode such as Slide Valve mode is sent
as an integer value that represents the mode it is in. For
example, a 0 is sent if it is in manual, or a 10 is sent if it
is in automatic, or a 20 is sent if it is in remote. The value
zero (0) is used to represent an OFF status and a DIS-
ABLED option. The value one (1), which is received as a
10, is used to represent an ON status and an ENABLED op-
tion. Only data values that are designated as setpoints are
modifiable. Read Only is used to help identify what data
is not modifiable. The setpoint range is checked to see
if it is an allowed setting. If it is not allowed, the setting
is not changed. Reference the Quantum™ Data Tables in
this manual for the address listing and description of data.
A command has been provided that selects whether data
to and from the Quantum™ will be returned in the units
that are the default (pressure in PSIA and temperature in
Degree C) or in the units that are selected to display at
the panel.
START ADD. FUNC.
STARTING
ADDRESS
# OF
REGISTERS
TO LOAD
CRC
CHECK
END
T1-T2-T3-T4 01 03 07 D3 00 01 * * T1-T2-T3-T4
* The CRC value is calculated by the transmitting
device, which appends the CRC to the message.
RTU Response Example
Using the RTU Read example just shown, a typical
response would look like:
START ADD. FUNC.
BYTE
COUNT TO
FOLLOW
ANSWER
CRC
CHECK
END
T1-T2-T3-T4 01 03 02 04 23 * * T1-T2-T3-T4
The returned value in the above example is 0423
hex. Converting this to decimal equates to 1059, and
assuming a decimal point gives an answer of 105.9
(PSIA or Panel units, depending on which has been
selected).
MODBUS® NOTES
This has been an example of how the Quantum™ HD uses
MODBUS® Protocol. It is hoped that the information pro-
vided here will assist the end user in writing applications
that will allow the Quantum™ to be implemented into
networks that the customer may already have in use.
This information is subject to change at any time, and is
provided as a reference only. Not all areas of the MOD-
BUS® Protocol can be handled in this document. Some
additional information regarding MODBUS® Protocol that
the end user should be aware of:
• There are many versions of MODBUS® Protocol
that are available, and an application that works
properly on one system, may not function identi-
cally on another.
• Some versions of MODBUS® Protocol may re-
quire the user to increment any referenced ad-
dresses by 1 (one). For instance, if you wanted
to look at Frick
®
Address 2003, you may need to
actually look at address 2004. The Quantum™
addressing begins at 0 (zero), whereas some
MODBUS® Protocols begin at 1 (one), therefore,
End of
message
Start of
message
Quantum™
ID
Function
03 = Read
07 = H. O. Address
D3 = L.O. Address
CRC Error
Correction
Code
00 = H.O. # of Data Registers
01 = L.O. # of Data Registers
End of
message
Start of
message
Quantum™
ID
Function
03 = Read
02 = 2 Bytes
CRC Error
Correction
Code
04 = H.O. Value
23 = L.O. Value
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