com.eurotech.framework.protocol.modbus
Class ModbusDataFormation

java.lang.Object
  com.eurotech.framework.protocol.modbus.ModbusDataFormation

public class ModbusDataFormation
extends Object

This static class defines the various data types and extended data implementations for Modbus. The Modbus specification only defines boolean and 16 bit analog data, many manufacturers have extended the protocol to handle 32 bit data, both as 32 bit integers and 32 bit IEEE floating point values. There are two variations in how this extension is done.

The first variation doesn't specifically break the protocol, but does create an unexpected response. In this variation, some registers are simply treated as 32 bit registers and so only require a single offset to specify a 32 bit register and value. The one "broken" response is in a read or write, the byte count will be 4 times the data count versus the "normal" two bytes to one data.

The other variation, in order to not break the very specifics of the protocol, implemented 32 bit data through register pairing. In register pairing, a pair of adjacent 16 bit registers, such as registers at offset 0 and 1 or offset 10 and 11, would be joined to construct the 32 bit value. This variation remains compatible with all intermediate equipment.

Note: Care must be taken in setting up data maps for this second variation. As each 32 bit value is represented by two consecutive registers, the Modbus offsets must be doubled relative to the contained data. In other words, 5 32 bit data values occupy 10 consecutive registers. If a data map specifies a data field starting at Modbus offset 100 and having 50 "PAIRED_32_BIT" values, the map will represent 100 registers at offsets 100 through 199 on the Modbus field device.

The Field values, not the field names should be used in configuration files.

Author:

matt.demaree

Field Summary

static String	BOOLEAN
static String	PAIRED_32_BIT
static String	SINGLE_16_BIT
static String	SINGLE_32_BIT

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BOOLEAN

public static final String BOOLEAN

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Constant Field Values

SINGLE_16_BIT

public static final String SINGLE_16_BIT

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Constant Field Values

PAIRED_32_BIT

public static final String PAIRED_32_BIT

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Constant Field Values

SINGLE_32_BIT

public static final String SINGLE_32_BIT

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Constant Field Values