Toptech MultiLoad II User Manual

Chapter 9 – Data Communication Notes and Recommendations
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CHAPTER 9 DATA COMMUNICATION NOTES AND RECOMMENDATIONS
This topic provides some basic communications concepts, as well as Toptech's recommendations for achieving
optimum performance.
9.1 PROTOCOL SELECTION: RS-232 VS. RS-485
9.1.1 RS-232
RS-232 communications protocol was designed for point-to-point (i.e., computer to a single device)
communications for short distances. The actual specification for RS-232 distance is limited to 50 feet. In
practice, however, RS-232 communications can be successful at distances over 1000 feet. We generally try to
limit distances to 500-600 feet. RS-232 requires a minimum of 3 wires: Transmit, Receive and Signal ground
wires. More wires are required for hardware handshaking. RS-232 can work on straight, non-twisted-pair wiring.
If existing wiring that is not twisted-pair must be used, then RS-232 protocol should be used.
9.1.2 RS-485
RS-485 communications protocol was designed for multi-point (i.e., computer to multiple devices, also called
multi-dropped) communications and can support distances over 5,000 feet. RS-485 requires 4 wires (2 twisted-
pair) for normal full-duplex communications. With special hardware, 2-wire half-duplex RS-485 can be
accomplished. RS-485 utilizes a transmit pair of wires (TDA and TDB) and a receive pair of wires (RDA and
RDB). A ground wire is not recommended normally, although some devices may have a terminal block for an
RS-485 ground. Most multi-dropped devices require RS-485 communications. When installing new wiring, RS-
485 twisted-pair wiring is preferred.
9.2 CABLE SELECTION
The speed and distance of communications is mostly affected by the capacitance and resistance of the wiring.
Copper wiring is generally low resistance, so this is not normally the limiting factor. Capacitance, however, can
vary greatly from one type of wire to another. In general, the larger the wire, the higher the capacitance. Wiring
size of 20 to 24 gauge is typically best for data communications. Capacitance of 16pf or less is preferred. With
16pf cable, 9600 baud communications can operate over 1000 feet for RS-232, and over 5000 feet for RS-485.
Doubling the capacitance will generally halve the baud rate or the distance.
Data communications cable should always be shielded. Individual wires or pairs do not need shielding, but an
overall shield should always be used. Whenever possible, always run data communications cable in conduit
and protected from moisture. Moisture can invade most cable coatings and disrupt data communications
integrity. For exposed routing or direct burial, Teflon coatings are recommended. Armored cable is also
available for running over-head without conduit.
RS-232 communications will work over almost any type of wiring, although speed and distance may be limited
by some wiring. Straight (individual) wires or twisted-pair wiring can be used. RS-485 communications requires
twisted-pair wiring with an impedance of 100 ohms.
For new installations, if you select wiring suitable for RS-485 wiring, it will always work for RS-232. This will
provide the ability to change from one communications protocol to another without replacing the wiring.
9.3 LINE TERMINATION IN MULTI-DROPPED COMMUNICATIONS
Toptech Systems has specialized hardware that will support multi-dropping of devices on a single RS-232
communication line. This is accomplished by tri-stating or disconnecting the transmitter of a device when it is
not transmitting on the communications line. This is similar to the RS-485 multi-dropping method. Due to the
tri-stating of the transmitters, the transmit circuit is 'floating' when no device is transmitting. This can sometimes
cause problems for the computer's receiver circuit, usually framing errors or break conditions.

Toptech MultiLoad II Specifications

General

Brand	Toptech
Model	MultiLoad II
Category	Control Systems
Language	English

Summary

CHAPTER 1 PROTOCOL SPECIFICATION

DEFINITIONS

Defines ASCII characters and protocol terms like BCC, LRC, CRC.

SMITH PROTOCOL

Describes the Smith protocol data format for host communications.

BROOKS PROTOCOL

Describes the Brooks protocol data format for host communications.

DANIELS PROTOCOL

Describes the Daniels protocol data format and message structure.

MODBUS-RTU PROTOCOL

Details the Modbus-RTU protocol implementation and message format.

MODBUS-TCP/IP PROTOCOL

Details the Modbus-TCP/IP protocol implementation and message format.

CHAPTER 2 MULTILOAD COMMAND RESPONSES

MODBUS COMMAND RESPONSES

Describes Modbus command status, RCU status, and card status data.

CHAPTER 3 QUERY COMMAND

CHAPTER 4 FUNCTION COMMANDS

REBOOT AND FACTORY RESET

Commands for software reboot and restoring factory defaults.

KEYPAD AND CONFIGURATION COMMANDS

Commands to manage keypad state and RCU configuration status.

HOST COMMUNICATION COMMANDS

Commands related to host system communication status and timeouts.

LOGGING AND PRINTER COMMANDS

Commands for EOD report printing and sending characters to the printer.

PRODUCT AND DATABASE CLEARING COMMANDS

Commands to clear product definitions, access IDs, and audit logs.

CHAPTER 5 TERMINAL COMMANDS

TERMINAL ESCAPE COMMANDS

Control codes for terminal display manipulation and input.

AUTHORIZE TRANSACTION

Command to authorize a MultiLoad transaction.

CLEAR RCU COUNTERS

Command to clear RCU counter values.

SETUP DATA ENTRY

Command to enable user input with a flashing cursor.

FONT AND COLOR SETTINGS

Commands to change font size and text foreground/background colors.

CURSOR AND DISPLAY CONTROL

Commands to home cursor, erase lines/screen, and clear display.

GRAPHIC AND TEXT DISPLAY COMMANDS

Commands to draw boxes, progress boxes, logos, and graphics with color.

CHAPTER 6 METER COMMANDS

TRANSACTION AND BATCH CONTROL

Commands for authorizing transactions, enabling presets, ending batches, and completing transactions.

STATUS AND ALARM REQUESTS

Commands to request status and alarms for presets, tanks, samplers, bays, components, and meters.

FLOW AND MESSAGING COMMANDS

Commands for controlling preset flow and displaying preset messages.

TRANSACTION MODES AND DATA RETRIEVAL

Commands for setting transaction modes and retrieving remote transaction data.

CHAPTER 7 REGISTER OPERATIONS

GENERIC REGISTER OPERATIONS AND DATA TYPES

Covers reading, updating registers, and various data type formats.

CONFIGURATION REGISTERS BY LEVEL

Details configuration registers for RCU, Bay, Preset, Meter, Component, Additive, Tank, Sampler, Security, Reports.

CUSTOM LOGIC AND BOL DEFINITIONS

Covers custom logic definitions, values, and standalone BOL definitions.

SPECIAL PURPOSE AND SYSTEM REGISTERS

Lists registers for firmware, date/time, network, GPS, language, and device databases.

CHAPTER 8 COMMUNICATION TRACE EXAMPLE

HOST SOFTWARE STARTUP PROCEDURES

Demonstrates startup steps like updating date/time and product definitions.

TRANSACTION AND BATCH AUTHORIZATION PROCESSES

Details the steps for driver card processing, transaction authorization, and batch authorization.

BATCH AND TRANSACTION COMPLETION

Explains procedures for monitoring load, ending batches, and concluding transactions.

HOST SOFTWARE SHUTDOWN

Describes the process for shutting down the host software.

CHAPTER 9 DATA COMMUNICATION NOTES AND RECOMMENDATIONS

PROTOCOL SELECTION: RS-232 VS. RS-485

Compares RS-232 and RS-485 protocols for data communication.

CABLE SELECTION

Discusses cable types and their impact on communication speed and distance.

LINE TERMINATION IN MULTI-DROPPED COMMUNICATIONS

Explains line termination for multi-dropped RS-232/RS-485.

OPTICAL ISOLATION

Recommends optical isolation devices for data lines against power fluctuations.

SHIELD GROUNDING

Details proper shielding and grounding for data communication cables.

CHAPTER 10 PARAMETER ACCESS SECURITY

UNDERSTANDING NEW USER AND SECURITY FEATURES

Introduces user and security features, including bypass switch, user creation, and security levels.