SERIAL COMMUNICATIONS INTERFACE
RS-485 Serial Communications
The optional RS-485 serial communication interface provides two-way communication between the controller and other compatible equipment such as a printer, PLC, HMI, or a host computer. In multipoint applications, each controller can be configured with a unique node address ranging from 0-99.
Through this serial interface, data from the controller can be interrogated or changed, alarm output(s) reset and Auto-tune invoked.
Since the same pair of wires are used for both transmit and receive, only one-way communication is possible at a time. The controller has a variable response time, to allow the host device adequate time to release the communication line after issuing a command to the controller.
Configuration Software
The Serial communications option is necessary to work with Red Lion
Control’s Windows based SFCRM software. This software allows for easy controller parameter configuration by computer. These settings can be saved to a disk file for later use or used for multi-controller down loading. On-line help is provided within the software.
Controller Configuration
The controller’s serial communication format is configured in Serial
Communication Program Module 6-SC using the front panel. Baud rate and character frame must be matched to the other communicating device. The node address parameter is a unique address number assigned to each slave unit on the bus.
Sending Commands And Data
When sending commands to the controller, a command string of ASCII characters must be constructed. The string varies in length depending on the nature of the command. At most, a command string consists of a Controller
(Node) Address number (not required for address of 0), a Command Code character, a Register Identification character (for most commands),
Numerical Data (if writing data to the controller) and ending with a string
Terminator of “*” or “$”. The controller will not respond with an error message to invalid commands.
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Sending Numeric Data
Data written to individual registers must be limited to the registers numerical data range (See Register Identification Table). If more digits are sent, the controller only accepts the last four digits of the numeric data.
Negative numbers must have a minus sign. The controller ignores any decimal point and conforms the number to the register identification resolution. (Example: “25” is written to the proportional band register. The value recorded by the register is now 2.5. If a value of 25% is intended, write a value of 25.0 or 250.
Controller (Node) Address
Code Description
N Controller Node
Address Specifier
Comments
Target a specific controller with the next
Command. Must be followed by a one or two digit (0-99) controller node address number. Not required for a node address of 0.
Commands Table
Code
T
V
Description
Read Value
(Transmit)
Write Value
(Change)
R Reset Alarm
C Control Action
P Print Block
Request
Comments
Read value register command. Must be followed by Register ID character A-M, BB, HC, or W.
Write value register command. Must be followed by Register ID character B-H or J-M and appropriate Numeric Data.
Write alarm register command. Must be followed by Register ID character G or H.
Write control register command. Must be followed by Register ID character S-U with
Numeric Data of 1 or 2.
Read block register command. Allows multiple reads with one command.
