Flachmann und Heggelbacher Docklight V2.2, User Manual

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Docklight V2.2 User Manual 07/2016 Copyright 2016 Flachmann und Heggelbacher GbR
Glossary / Terms Used
Two different serial transmission modes for MODBUS are defined: "RTU mode" for 8 bit
binary transmissions, and "ASCII mode". "RTU mode" is the default mode that must be
implemented by all devices.
See http://www.modbus.org for a complete specification of the MODBUS protocol.
11.10 Multidrop Bus (MDB)
Multidrop Bus (MDB) is a more exotic RS232/RS485 application, used for example in
vending machine controllers, which requires a 9 bit compliant UART. The 9th data bit is
used for selecting between an ADDRESS and a DATA mode.
A way to monitor and simulate such communication links using standard 8-bit UARTs,
i.e. standard RS232-to-USB converters, is to use
temporary parity changes .
See also Wikipedia on MDB and the original MDB 3.0 specification for more information
and details.
11.11 Receive Sequence
A Receive Sequence is a sequence that can be detected by Docklight within the
incoming serial data. A Receive Sequence is specified by
1. an unique name (e.g. "Modem Answer OK"),
2. a character sequence (e.g. "6F 6B 13 10" in HEX format),
3. an
action that is triggered when Docklight receives the defined sequence.
11.12 RS232
The RS232 standard is defined by the EIA/TIA (Electronic Industries Alliance /
Telecommunications Industry Associations). The standard defines an asynchronous
serial data transfer mechanism, as well as the physical and electrical characteristics of
the interface.
RS232 uses serial bit streams transmitted at a predefined baud rate. The information is
separated into characters of 5 to 8 bits lengths. Additional start and stop bits are used
for synchronization, and a parity bit may be included to provide a simple error detection
mechanism.
The electrical interface includes unbalanced line drivers, i.e. all signals are represented
by a voltage with reference to a common signal ground. RS232 defines two states for the
data signals: mark state (or logical 1) and space state (or logical 0). The range of
voltages for representing these states is specified as follows:
Signal State Transmitter Voltage
Range Receiver Voltage
Range
Mark (logical 1) -15V to -5V -25V to -3V
Space (logical 0) +5V to +15V +3V to +25V
Undefined -5V to +5V -3V to +3V
The physical characteristics of the RS232 standard are described in the section RS232
Connectors / Pinout