QUANTUM
™
LX EVAPORATOR CONTROL PANEL
COMMUNICATIONS SETUP
090.610-CS (MAY 2016)
Page 25
QUANTUM
™
LX ALLEN-BRADLEY COMMUNICATION
This section contains programming examples for read-
ing data from and writing data to the Frick Quantum
control panel from an Allen Bradley (AB) SLC500 or PLC5
processor. Allen Bradley (AB) RSLogix500 programming
software has been used for the following examples,
however, these examples can also be used for the AB
RSLogix5 software.
Overview Of Half And Full Duplex Theory
To provide for the reading and writing of data to
Quantum™ LX panels using Allen-Bradley commu-
nication, the Quantum™ LX has an Allen-Bradley
DF1 communication driver that recognizes either
half or full duplex SLC 500 protected typed logical
read and write commands (either half or full duplex
must be selected). Half-duplex simply means that
data can only be sent in one direction at a time
(the concept of how a walkie-talkie works). Using
full-duplex, data can be sent and received simulta-
neously (the concept of how a telephone works).
This is a Master / Slave multi-drop communication
method.
The Quantum™ LX talks Allen-Bradley SLC protocol
and is programmed to resemble an Allen-Bradley
SLC500 slave station. The customer’s PLC or DCS
must be setup to initiate the reading and writing of
data to a Quantum™ LX. The Quantum™ LX does
not initiate any communications. The panel ID num-
ber is used as its station address and the target
node. With the AB PLC, the MSG (Message) instruc-
tion is used to send read and write requests. A DCS
(Distributed Control System) will use a SLC 500 DF1
protocol driver to send protected typed logical read
with 3 address elds and protected typed logical
write requests with 3 address elds to a Quantum™
LX. Fifty (50) data elements can be read with one
read.
Setpoints are changed by sending a write command
to one element. Changing a setpoint causes the
Quantum™ LX to save the new setpoint to Flash
memory (non-volatile memory).
Be careful not to continuously request a setpoint
change. It is to be expected that communica-
tions may slow down during the process of writ-
ing setpoints or clearing alarms. Both of these
processes involve writing to either EEPROM or
Flash Memory and does take some time. If com-
munication requests are being sent faster than
once every couple of seconds, there will be tem-
porary slowdowns during these processes.
SECTION 3
QUANTUM™ LX ALLEN-BRADLEY COMMUNICATION
Additionally, keeping the Quantum™ LX busy writing to
Flash memory will interfere with the communications
to its I/O Boards. A communication failure to an I/O
board will cause the Evaporator to shutdown. Control
commands are also sent with a write command. For
more detail and a list of the data, reference the Quan-
tum™ LX Data Table section. For details about the ac-
tual protocol, reference the AB publication 1770-6.5.16
DF1 Protocol and Command Set Reference Manual.
Because overrun can occur, the baud rate and com-
mands should be setup to produce the most desired
throughput. The master station should have the Stop
Bit and Parity set to match the Quantum™ LX, Dupli-
cate Detect disabled, and Error Detect set for BCC or
CRC.
When communication is between either your program-
ming software and a Quantum™ LX or an Allen-Brad-
ley PLC and a Quantum™ LX on a multi-drop link, the
devices depend on a DF1 Master to give each of them
polling permission to transmit in a timely manner. As
the number of Quantum™ LX slaves increase on the
link, the time between when each panel is polled also
increases. This increase in time may become larger if
you are using low baud rates. As these time periods
grow, the timeouts such as the message timeout, poll
timeout and reply timeout may need to be changed to
avoid loss of communication.
ACK Timeout - The amount of time in 20 milliseconds
increments that you want the processor to wait for an
acknowledgment to the message it has sent before the
processor retries the message or the message errors
out.
Reply Message Wait Time - Dene the amount of
time in 20 millisecond increments that the master sta-
tion will wait after receiving an ACK (to a master-ini-
tiate message) before polling the remote station for a
reply. Choose a time that is, at minimum, equal to the
longest time that a remote station needs to format a
reply packet. Some remote stations can format reply
packets faster than others.
Message Timeout - Denes the amount of time in sec-
onds that the message will wait for a reply. If this time
elapses without a reply, the error bit is set, indicating
that the instruction timed out. A timeout of 0 seconds
means that there is no timer and the message will wait
indenitely for a reply. Valid range 0-255 seconds.
Note: Make sure the Allen-Bradley PLC and the pro-
gramming software is the most recent software revi-
sion. Some revisions have been made that do not allow
the SLC Typed Logical Read/Write Message Command.
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