Frick QUANTUM LX - ASCII Query (Read) Example

QUANTUM
™
LX EVAPORATOR CONTROL PANEL
COMMUNICATIONS SETUP
090.610-CS (MAY 2016)
Page 39
dress eld) is received, each device de-
codes it to 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 inter-
val. The entire message frame must be
transmitted as a continuous stream. If a
silent interval of more than 1.5 character
times occurs before completion of the
frame, the receiving device ushes the
incomplete message and assumes that
the next byte will be the address eld of
a new message.
Similarly, if a new message begins ear-
lier than 3.5 character times following a
previous message, the receiving device
will consider it a continuation of the pre-
vious message. This will set an error, as
the value in the nal CRC eld will not be
valid for the combined messages. A typi-
cal 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
The examples that follow are based on compres-
sor addresses, but may be modied using the
Evaporator addresses that are shown in the Data
Tables that appear later in this manual. To demon-
strate how an address within the Quantum™ may
be read, the following test can be performed us-
ing Windows HyperTerminal (NOTE: Hyperterminal
cannot be used to test RTU or TCP/IP):
As an example, a MODBUS® command will be
created and sent to obtain the actual Discharge
Pressure value of a compressor. Using the ad-
dress tables found later in this manual, locate the
address for Discharge Pressure. In this case, it is
Frick® Address 2003 (decimal). 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
understand how the address that we are re-
questing is arrived at. We want to know the ac-
tual value of the Discharge Pressure, Frick® Ad-
dress 2003 (decimal).
The 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 Quan-
tum™ panels on the MODBUS® network will
become active, communications-wise, once the
Colon appears. Next, the panels will look at the
rst byte following the Colon ( : ). If this byte
equals the Panel ID # of the particular Quantum™
being queried, it will immediately 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