Table of Contents
Advertisement
QUANTUM™ HD ALLEN-BRADLEY COMMUNICATION
QUANTUM™ HD ALLEN-BRADLEY COMMUNICATION
This section contains programming examples for reading
data from and writing data to the Frick Quantum control
panel from an Allen Bradley (AB) SLC500 or PLC5 proces-
sor. Allen Bradley (AB) RSLogix500 programming soft-
ware 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™ HD panels using Allen-Bradley communi-
cation, the Quantum™ HD 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 simultaneously (the concept
of how a telephone works). This is a Leader / Fol-
lower multi-drop communication method.
The Quantum™ HD talks Allen-Bradley SLC protocol
and is programmed to resemble an Allen-Bradley
SLC500 follower station. The customer's PLC or DCS
must be setup to initiate the reading and writing of
data to a Quantum™ HD. The Quantum™ HD 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) instruction is
used to send read and write requests. A DCS (Dis-
tributed Control System) will use a SLC 500 DF1 pro-
tocol driver to send protected typed logical read with
3 address fields and protected typed logical write re-
quests with 3 address fields to a Quantum™ HD. Fifty
(50) data elements can be read with one read.
Setpoints are changed by sending a write com-
mand to one element. Changing a setpoint causes
the Quantum™ HD 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 communications
may slow down during the process of writing set-
points or clearing alarms. Both of these processes
involve writing to either EEPROM or Flash Memory
and does take some time. If communication re-
quests are being sent faster than once every cou-
ple of seconds, there will be temporary slowdowns
during these processes.
Additionally, keeping the Quantum™ HD busy writing
QUANTUM™ HD COMPRESSOR CONTROL PANEL
COMMUNICATIONS SETUP
SECTION 3
to Flash memory will interfere with the communica-
tions to its I/O Boards. A communication failure to
an I/O board will cause the compressor to shutdown.
Control commands such as starting the compressor
are also sent with a write command. For more detail
and a list of the data, reference the Quantum™ HD
Data Table section. For details about the actual pro-
tocol, 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 leader station should have the Stop
Bit and Parity set to match the Quantum™ HD, Du-
plicate Detect disabled, and Error Detect set for BCC
or CRC.
When communication is between either your pro-
gramming software and a Quantum™ HD or an Allen-
Bradley PLC and a Quantum™ HD on a multi-drop
link, the devices depend on a DF1 Leader to give each
of them polling permission to transmit in a timely
manner. As the number of Quantum™ HD followers
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 millisec-
onds 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 mes-
sage errors out.
Reply Message Wait Time - Define the amount of
time in 20 millisecond increments that the leader sta-
tion will wait after receiving an ACK (to a leader-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 - Defines the amount of time in
seconds that the message will wait for a reply. If this
time elapses without a reply, the error bit is set, in-
dicating that the instruction timed out. A timeout
of 0 seconds means that there is no timer and the
message will wait indefinitely 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 re-
vision. Some revisions have been made that do not
090.040-CS (JAN 14)
Page 33
Advertisement
Table of Contents
