Johnson Controls Frick QUANTUM LX, Setup

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QUANTUM™ LX COMPRESSOR CONTROL PANEL
COMMUNICATIONS SETUP
090.020-CS (APRIL 13)
Page 46
The following user selectable button is provided:
• [Refresh]
This screen allows the technician to view the ModBus
TCP data communications information that the Quan-
tum™ LX is receiving and transmitting.
Each time a new command is sent or received, the
screen will need to be refreshed by selecting the [Re-
fresh] button.
The top line of data is the most recent activity. At the
left of each line, you should see whether the data is
IN or OUT (Response or Command), and the actual
data (in Hexadecimal format). This information can
be used to compare against the data being sent and
received at the other end of the communications link,
to verify proper operation.
Refer to the following table for an example of how
the data packets are created, using the data that has
been shown on the above screen.
Byte Count in data returned
Data in register 2000
Data in register 2001
Response 01 Out: 00
.
00 00
.
00 00
.
07 01 03 04 00
.
20 00
.
16
Command 00 In: 00 . 00 00 . 00 00 . 06 01 03 07 . D0 00 . 02
# of registers to read
Address of
fi rst register (2000)
Read Holding register
Modbus ID
# of bytes in command
Always 0 for Modbus TCP
Transaction Identifer
MODBUS® ASCII (Serial Communications)
In the ASCII Transmission Mode (American Standard
Code for Information Interchange), each character
byte in a message is sent as 2 ASCII characters. This
mode allows time intervals of up to a second between
characters during transmission without generating
errors. Some particulars about MODBUS® ASCII:
• The device address fi eld of the message
frame contains two characters (16 bits).
• The function code fi eld of the message
frame will contain two characters (16 bits).
• Word size is selectable.
• Error checking is accomplished using LRC
(Longitudinal Redundancy Check).
• Hyperterminal can be used to test commu-
nications.
MODBUS® RTU (Serial Communications)
In RTU (Remote Terminal Unit) Mode, each 8-bit
message byte contains two 4-bit hexadecimal char-
acters, and the message is transmitted in a continu-
ous stream. The greater effective character density
increases throughput over ASCII mode at the same
baud rate. Some particulars about MODBUS® RTU:
• The device address fi eld of the message
frame contains 8 binary bits.
• The function code fi eld of the message
frame will contain 8 binary bits
• Word size is selectable.
• Error checking is accomplished using CRC
(Cyclical Redundancy Check).
• Hyperterminal cannot be used to test com-
munications.
Serial Port Configuration Of The Leader
7 or 8 Bits per Character (Data Bits)
Odd, Even or No Parity
1 or 2 Stop Bits
No Handshake
Data Packet
The MODBUS® protocol establishes the format
for the
Leader's
query by creating a message (data
pack-et) as follows:
• Assign the device address (Quantum™ panel