GE 1601-0149-A2 manual Modbus Functions

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Modbus Functions

 

 

489

 

 

 

 

Communications Guide

 

CRC-16 Algorithm

 

 

 

Once the following algorithm is complete, the working register “A” will contain the

 

CRC value to be transmitted. Note that this algorithm requires the characteristic

 

polynomial to be reverse bit ordered. The MSbit of the characteristic polynomial is

 

dropped since it does not affect the value of the remainder.

 

The symbols used in the algorithm are shown below:

 

-->

data transfer

 

A; Alow; Ahigh

16-bit working register; low and high order bytes of A (the 16-bit

 

 

working register)

 

CRC

16 bit CRC-16 result

 

i, j

loop counters

 

(+)

logical EXCLUSIVE-OR operator

 

N

total number of data bytes

 

Di

i-th data byte (i = 0 to N – 1)

 

G

16 bit characteristic polynomial = 1010000000000001 (binary)

 

 

with MSbit dropped and bit order reversed

 

shr (x)

right shift operator (the LSbit of x is shifted into a carry flag, a '0' is

 

 

shifted into the MSbit of x, all other bits are shifted right one

 

 

location)

The CRC algorithm is shown below:

1.FFFF (hex) --> A

2.0 --> i

3.0 --> j

4.Di (+) Alow --> Alow

5.j + 1 --> j

6.shr (A)

7.Is there a carry? No: go to step 8.

8.

Is j = 8?

Yes: G

(+) A --> A

and continue.

No: go

to

5.;

Yes: continue.

9.

i

+ 1

--> i

No: go

to

3.;

Yes: continue.

10.

Is i = N?

11.

A

-->

CRC

 

 

 

 

 

Timing Data packet synchronization is maintained by timing constraints. The receiving device must measure the time between the reception of characters. If three and one half character times elapse without a new character or completion of the packet, then the communication link must be reset (i.e. all slaves start listening for a new transmission from the master). Thus at 9600 baud a delay of greater than 3.5 ⋅ 1 / 9600 ⋅ 10 = 3.65 ms will cause the communication link to be reset.

Modbus Functions

Supported Functions The following functions are supported by the 489:

•Function Codes 03 and 04: Read Setpoints and Actual Values

•Function Code 05: Execute Operation

•Function Code 06: Store Single Setpoint

•Function Code 07: Read Device Status

•Function Code 08: Loopback Test

•Function Code 16: Store Multiple Setpoints

A detailed explanation of how the 489 implements these function codes is shown in the following sections.

GE Multilin

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Contents 489 Page Table of Contents Table of Contents Electrical Interface Modbus RTU Description Copyright 2004 GE MultilinGE Multilin Modbus Functions Message Format and Example ValuesModbus Functions Function Code Request status from slave Modbus Functions Function Code 16 Store Multiple Setpoints Illegal Data Address Error ResponsesEvent Recorder Memory Map InformationWaveform Capture Dual Setpoints Passcode Operation 489 Memory Map Sheet 1 489 Memory Map Sheet 2 Addr Name Range Step Units Format DefaultStatus / Trip Pickups 489 Memory Map Sheet 3 Status / Alarm PickupsMetering Data / Current Metering 489 Memory Map Sheet 4Status / Digital Inputs Status / Real Time ClockMetering Data / Voltage Metering Metering Data / Power MeteringMetering Data / Temperature 489 Memory Map Sheet 5489 Memory Map Sheet 6 Learned Data / Analog in MIN/MAX Maintenance / Trip CountersMaintenance / General Counters 489 Memory Map Sheet 7489 Memory Map Sheet 8 489 Memory Map Sheet 9 Digital Inputs / General Input E 489 Memory Map Sheet 10Digital Inputs / General Input C Digital Inputs / General Input D489 Memory Map Sheet 11 489 Memory Map Sheet 12 489 Memory Map Sheet 13 Current Elements / Negative Sequence 489 Memory Map Sheet 14Current Elements / Ground O/C 489 Memory Map Sheet 15 Current Elements / Ground Directional Current Elements / Phase DifferentialCurrent Elements / HIGH-SET Phase Overcurrent 489 Memory Map Sheet 16489 Memory Map Sheet 17 Voltage Elements / Distance Element 489 Memory Map Sheet 18Voltage Elements / Neutral Overvoltage Fundamental Voltage Elements / Loss of Excitation489 Memory Map Sheet 19 489 Memory Map Sheet 20 489 Memory Map Sheet 21 Thermal Model / Model Setup RTD Temperature / RTD #12RTD Temperature / Open RTD Sensor RTD Temperature / RTD SHORT/LOW Temperature489 Memory Map Sheet 23 489 Memory Map Sheet 24 489 Memory Map Sheet 25 Analog INPUT/OUTPUT / Analog Input 489 Memory Map Sheet 26Testing / PRE-FAULT Setup Testing / Simulation Mode489 Memory Map Sheet 27 489 Memory Map Sheet 28 489 Memory Map Sheet 29 Waveform Memory SetupWaveform Memory Samples Decimal Places Code Type DefinitionUnsigned Value Decimal PlaceALARM/TRIP Status SwitchAlarm / Trip Type Reset ModeOvercurrent Curve Input SwitchAnalog Output ParameterData Formats Sheet 7 Order Code Simulation ModeCurve Reset Type Switch StatusAssignable Input Undervoltage TripElement Type Breaker OperationDNP Protocol DNP 3.0 Device Profile Document DNP Implementation Table Default VariationsVariation Binary Inputs Sheet 2 Binary Input / Binary01/02 Binary Inputs Sheet 1Binary Inputs Sheet 4 Binary Inputs Sheet 310/12 Binary / Control RelayBinary Output Point List Counters Point List DNP Point Lists Binary / Frozen Counter Objects 20/21Assigned to Analog Inputs Point List Sheet 1Impedance angle Analog Inputs Point List Sheet 2Analog Inputs Point List Sheet 3 Table Notes Analog Inputs Point List Sheet 4Index GE Multilin
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