Laurel Electronics Custom ASCII Protocol For Laureate Series 2 Digital Panel Meters, Counters, Timers & L-Series Transmitters - Manual (Page 3)

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2. INTRODUCTION, CUSTOM ASCII SERIAL PROTOCOL
The Custom ASCII Protocol is a simple serial communications protocol which is optimized for use
with our programmable digital panel meters, counters, timers and transmitters.
Digital panel meters, counters and timers accept an optional serial communications plug-in
board, which can be any of the following:
• RS232 board
• RS485 board with dual RJ11 jacks.
• RS485 board with dual RJ45 jacks
• USB board
• USB-to-RS485 converter board
• Ethernet board
• Ethernet-to-RS485 converter board
Our two RS485 meter boards use the same circuitry and support the same serial protocols. The
boards with dual RJ11 jacks can be daisy-chained using readily available, straight-through 6-wire
data cables (not 4-wire telephone cables or crossover cables). Dual RJ45 jacks are available for
use with Modbus, as recommended in the Modbus Specification. With either board, the two jacks
are wired in parallel to allow daisy chaining of meters with no need for a hub. External repeaters
can be used to increase the number of addressable meters.
Our USB-to-RS485 and Ethernet-to-RS485 converter boards allow the host meter to function as a
normal meter, be connected to a host computer or Ethernet local area network (LAN), and also act
as the device server for an RS485 network of up to 31 meters. These should be equipped with
RS485 board with RJ11 connectors for daisy chaining with 6-wire data cables.
Our DIN-rail transmitters come with either an Ethernet or RS232/RS485 I/O port as ordered. This
is in addition to a scalable 4-20 mA output and dual relays, which are standard.
Our DIN-rail Ethernet-to-RS485 device server provides an RJ45 jack for connection to the
Ethernet, an RJ11 jack to support an RS485 network of meters, plus screw terminals to support
an RS485 network of DIN-rail transmitters via a set of 3 or 5 parallel wires (half- or full-duplex).
The Modbus Protocol, described in a different manual, is a software-selectable alternative to the
Custom ASCII Protocol. It is fully compliant with Modbus over Serial Line Specification V1.0
(2002). It is an industry standard which allows devices by different manufacturers to be digitally
addressed on the same network. However, it is more complex than the Custom ASCII Protocol
and is only recommended when Modbus compatibility is required. In Ethernet networks, the
Modbus TCP protocol is seamlessly converted to Modbus RTU or Modbus ASCII by our Ethernet
software. Note: Modbus is not supported by our weight meter.