Johnson Controls Frick QUANTUM LX, Setup

Page: 49 / 140

QUANTUM™ LX COMPRESSOR CONTROL PANEL
COMMUNICATIONS SETUP
090.020-CS (APRIL 13)
Page 49
The allowable characters transmitted for all
fi elds are hexadecimal 0–9, A–F. Networked
devices monitor the network bus continu-
ously, including during the ‘silent’ intervals.
When the fi rst fi eld (the address fi eld) is re-
ceived, each device decodes it to fi nd out if
it is the addressed device.
Following the last transmitted character,
a similar interval of at least 3.5 character
times marks the end of the message. A new
message can begin after this interval. The
entire message frame must be transmitted
as a continuous stream. If a silent interval
of more than 1.5 character times occurs be-
fore completion of the frame, the receiving
device fl ushes the incomplete message and
assumes that the next byte will be the ad-
dress fi eld of a new message.
Similarly, if a new message begins earlier
than 3.5 character times following a previ-
ous message, the receiving device will con-
sider it a continuation of the previous mes-
sage. This will set an error, as the value in
the fi nal CRC fi eld will not be valid for the
combined messages. A typical message
frame is shown below:
START ADDRESS FUNCTION DATA
LRC
CHECK
END
T1-T2-T3-T4 8 Bits 8 Bits
N x 8
Bits
16 Bits T1-T2-T3-T4
ASCII Query (Read) Example
To demonstrate how an address within the Quan-
tum™ may be read, the following test can be per-
formed using Windows HyperTerminal (NOTE: Hyper-
terminal cannot be used to test RTU or TCP/IP):
As an example, a MODBUS® command will be cre-
ated and sent to obtain the actual Discharge Pressure
value of a compressor. Using the address tables found
later in this manual, locate the address for Discharge
Pressure. In this case, it is Frick® Address 2003 (dec-
imal). Since this is the only address we are interested
in obtaining the value of, send the following message:
: 01 03 07 D3 00 01 21 CRLF
Where:
Message Start:
Quantum™ ID #:
Read Function:
H. O. address (hex):
L. O. address (hex):
H. O. # of Data Registers:
L. O. # of Data Registers:
Error Correction Code:
Carriage Return - Line Feed:
Look at this message on a more basic level, to un-
derstand how the address that we are requesting is
arrived at. We want to know the actual value of the
Discharge Pressure, Frick® Address 2003 (decimal).
The fi rst part of the message will be a Colon (:). This
represents a heads up alert that data is coming:
: 01 06 1B EE 03 E8 05 CRLF
Where:
Message Start:
Quantum™ ID #:
Write Function:
H. O. address (hex):
L. O. address (hex):
H. O. # of Data Value:
L. O. # of Data Value:
Error Correction Code:
Carriage Return - Line Feed:
}
Any time that a message is sent, all of the Quantum™
panels on the MODBUS® network will become ac-
tive, communications-wise, once the Colon appears.
Next, the panels will look at the fi rst byte following
the Colon ( : ). If this byte equals the Panel ID # of
the particular Quantum™ being queried, it will imme-
diately fi nish reading the remainder of the message.
If the byte does not equal its ID #, the message will
be ignored.
: 01 06 1B EE 03 E8 05 CRLF
Where:
Message Start:
Quantum™ ID #:
Write Function:
H. O. address (hex):
L. O. address (hex):
H. O. # of Data Value:
L. O. # of Data Value:
Error Correction Code:
Carriage Return - Line Feed:
}
00 = H. O. Address
87 = L. O. Address
00 = H. O. # of data registers
01 = L. O. # of data registers
End of
message
CRC Error
Correction
Code
Start of
message
Quantum™
ID
Function