Laurel Electronics LTSE6 - Manual - Manual (Page 20)

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10. CUSTOM ASCII PROTOCOL TRANSMITTER COMMUNICATIONS
All setup parameters are entered into the transmitter via Instrument Setup (IS) software, including
the serial communication format, digital address, operating mode, analog output scaling, and relay
operating modes and setpoints.
1. SERIAL COMMUNICATION FORMAT
The Custom ASCII serial communication format for both RS232 and RS485 is the following:
Modes...............Full Duplex (separate transmit and receive lines) or Half Duplex (RS485 only).
Baud Rate .........300, 600, 1200, 2400, 4800, 9600, 19200 selectable with IS software.
Data Format ......8 data bits, no parity, 1 stop bit
2. DATA FORMAT
The basic input data format consists of 9 or 10 ASCII characters, such as +9999.99A. The
first character is always a plus or minus sign. There are 6 numeric digits. A decimal point is always
required, even when it follows the last digit. The letter A is an optional alarm character. is the
carriage return character. A line feed character at the end of the string is ignored.
3. NETWORK CONFIGURATIONS
Using the Custom ASCII protocol, serial input transmitters can operate in a point-to-point mode
using RS232 or RS485, or in a multi-point mode using RS485:
The point-to-point mode is a direct connection between a computer (or other digital device) and
the transmitter. It is suggested that address 1 be selected for the point-to-point mode.
The multi-point mode is a connection from a host computer to multiple transmitters bused
together with their inputs and outputs connected in parallel. It is necessary to set up each device
on the bus with a different address from 1 to 31. To command a particular device, its address is
used in conjunction with the command, and only that device will respond. The outputs of all
devices on the bus are set to a high impedance state, except the device being addressed. Zero (0)
is a special address to which a device responds only internally (e.g. Reset), but it does not transmit
any response on the output lines. All devices may be commanded simultaneously with a 0 address,
and there will not be any output response contention.
4. OPERATING MODES
The serial input transmitter has three serial input modes, which are dedicated to the analog output
and relays based on serial data received via RS232 or RS485:
Remote A ........ Addressable remote units (up to 31 units)
Remote S ........ Single remote unit
Remote C ........ Single remote unit programmed to select specific data from a data string.