Download PowerWizard MODBUS Manual v0_8 2005-Jun-29 PDF

TitlePowerWizard MODBUS Manual v0_8 2005-Jun-29
TagsBit String (Computer Science) Network Packet Error Detection And Correction Byte
File Size375.3 KB
Total Pages87
Document Text Contents
Page 1

PowerWizard Modbus Manual – DRAFT Version0.8 1


Caterpillar Inc.
Non-Confidential

Contents

1 INTRODUCTION........................................................................................2

2 WIRING......................................................................................................2

2.1 Line Termination ................................................................................................. 3
2.2 Line Polarization ................................................................................................. 3

3 DATA LINK LAYER...................................................................................4

3.1 Data Structure..................................................................................................... 4
3.2 Communication ................................................................................................... 4
3.3 Supported Function Codes................................................................................. 5

4 ERROR CHECKING ..................................................................................6

4.1 Parity Check........................................................................................................ 6
4.2 Cyclic Redundancy Check.................................................................................. 7
4.3 Exception Responses ......................................................................................... 7
4.4 Fault Identifiers (FID) .......................................................................................... 8

5 REDUCED POWER MODE .......................................................................9

6 PARAMETER INFORMATION BY FUNCTION.........................................9

6.1 Data Link Security............................................................................................... 9
6.2 Spare Analog Input ........................................................................................... 11
6.3 Digital Selectors ................................................................................................ 15
6.4 Discrete Inputs and Outputs Monitoring........................................................... 20
6.5 Generator AC Parameters ................................................................................ 25
6.6 External Device Parameters............................................................................. 33
6.7 Generator Set State Control ............................................................................. 42
6.8 Timers and Counters ........................................................................................ 46
6.9 Emergency Shutdown Override........................................................................ 49
6.10 Event System.................................................................................................... 50
6.11 Engine Monitoring ............................................................................................. 52
6.12 POWERWIZARD Setpoints.............................................................................. 52
6.13 Miscellaneous ................................................................................................... 54

APPENDICES.....................................................................................................55

Appendix A Programming Examples ....................................................................... 55
Appendix B Blocks for Setpoint Configuration ......................................................... 57
Appendix C Setpoint Information for Setpoint Configuration ................................... 58
Appendix D Setpoint Value Lists .............................................................................. 75
Appendix E BitMask Value Lists............................................................................... 82
Appendix F Quick Reference Chart of Modbus Registers....................................... 83
Appendix G Glossary of Terms................................................................................. 86

Page 2

PowerWizard Modbus Manual – DRAFT Version0.8 2


Caterpillar Inc.
Non-Confidential

1 Introduction
The SCADA Data Link is supported by the PowerWizard2.0 and higher.

The PowerWizard2.0 and PowerWizard3.0 have a Supervisory Control and Data
Acquisition (SCADA) communications link between the controller and a host device
using the Modbus protocol. The host device is able to remotely monitor or control the
genset package equipped with the PowerWizard control panel in much the same way an
operator does from the panel.

The host device connects to the PowerWizard through a half-duplex RS-485 serial link.
The data is transmitted in a binary format over the serial connection. The host device
acts as Modbus Master, and the PowerWizard electronic controller acts as the Modbus
Slave, also called a Remote Transmitter Unit (RTU). The host device initiates all
communication, sending commands or requests for information to the PowerWizard
control. The PowerWizard control then takes action based on the query and/or sends a
response to the query over Modbus.

Various data rates are available, and can be configured on the control under SCADA
Network Configuration. The options are the following: 2400, 4800, 9600, 14400, 19200,
28800, 38400, 57600, and 115200 baud.


2 Wiring
The SCADA communication wires are brought out of the PowerWizard as part of the 70-
pin AMP connector. The pins, as designated on the AMP connector, are shown in Table
1.
Table 1: 70-pin Connector Modbus pins

Pin # Name Description

3 MODBUS – Optically isolated half-duplex differential (-) for Modbus
4 MODBUS Reference Half-duplex RS-485 Reference for Modbus
5 MODBUS + Optically isolated half-duplex differential (+) for Modbus




Modbus data transmission over RS-485 is accomplished over a single (ideally, twisted)
pair for differential signaling with transmit and receive alternating over the same wire pair
(MODBUS+ and MODBUS-). The Reference should be connected to the shield, to
prevent ground loop currents. Figure 1 shows a possible wiring configuration to a RS-
485 device. Figure 2 shows a possible wiring configuration to a RS-485 to RS-232
converter.

Page 43

PowerWizard Modbus Manual – DRAFT Version0.8 43


Caterpillar Inc.
Non-Confidential

Resolution Offset Data Range
1 / bit 0 0 to 1


Bit Definitions:
00 = FALSE
01 = TRUE


Engine Operating Mode
$012D (301) - 1 register (2 bytes) long - Read
Indicates current desired mode of operation of the engine.
This parameter indicates the status corresponding to the Run, Auto, and Stop keys on
the control. To change the operating mode, see the Engine Operating Mode Command
parameter.


Resolution Offset Data Range
1 / bit 0 0 to 2


Bit Definitions:
00 ($0000) = STOP
01 ($0001) = AUTO
10 ($0002) = RUN


Engine Operating Mode Command
$012E (302) - 1 register (2 bytes) long - Write
SCADA command to change of desired mode of operation of the engine.
Setting this has the same functionality as pressing the corresponding key (Run, Auto, or
Stop) on the control. To read the current mode, see the Engine Operating Mode
parameter.


Resolution Offset Data Range
1 / bit 0 0 to 2


Bit Definitions:
00 ($0000) = STOP
01 ($0001) = AUTO
10 ($0002) = RUN


Engine Status
$041D (1053) - 1 register (2 bytes) long - Read
Current operating state of the engine.


Resolution Offset Data Range
1 / bit 0 0 to 5


Bit Definitions:
000 ($0000) = NOT READY TO GO
001 ($0001) = GOING IN AUTO
010 ($0002) = GOING IN RUN

Page 44

PowerWizard Modbus Manual – DRAFT Version0.8 44


Caterpillar Inc.
Non-Confidential

011 ($0003) = READY IN AUTO
100 ($0004) = STOPPING IN AUTO
101 ($0005) = STOPPING NOT READY TO GO


Engine Protection has Shut Down Engine from Data Link
$04FB (1275) - 1 register (2 bytes) long - Read
Indicates that the engine protection system has shut down the engine, as opposed to the
engine shutting down based on an external command.


Resolution Offset Data Range
1 / bit 0 0 to 1


Bit Definitions:
00 = FALSE
01 = TRUE


Cooldown Duration Remaining
$041E (1054) - 1 register (2 bytes) long - Read
Time remaining in cooldown until engine is stopped.


Resolution Offset Data Range
1 second / bit 0 seconds 0 to 64255 seconds



Remote Initiate Command
$041F (1055) - 1 register (2 bytes) long - Write
When the control is in Auto mode, this commands the engine to Run when active and
Stop when inactive.
This can also be assigned to a switch for digital input. If so, either the digital input or this
SCADA command being true will trigger an automatic start if the control is in the Auto
mode. This SCADA command is unaffected by the digital input state configuration.


Resolution Offset Data Range
1 / bit 0 0 to 1


Bit Definitions:
00 = FALSE
01 = TRUE


Emergency Stop Command
$0420 (1056) - 1 register (2 bytes) long - Write
Will cause the engine to immediately stop without cooling down.
This is also assigned to a switch for digital input. If so, either the digital input or this
SCADA command being true will trigger an emergency stop event. This SCADA
command is unaffected by the digital input state configuration.


Resolution Offset Data Range
1 / bit 0 0 to 1

Page 86

PowerWizard Modbus Manual – DRAFT Version0.8 86


Caterpillar Inc.
Non-Confidential

1 Temperature of liquid found in engine cooling system.
$00CA Battery Voltage 6.13

1 Measured electrical potential of the battery at the control.
$00CB Engine rpm 6.11

1
Actual engine speed, calculated over a minimum

crankshaft angle of 720 degrees divided by the number of
cylinders.



$00CC Engine Operating Hours 6.8
2 Accumulated time that the engine is running.

$00CE Automatic Start/Stop State 6.7
1 Current state of the Automatic Start/Stop sequence.

$00CF Spare Analog Input Percentage 6.2

1 Percentage of full scale measured by auxiliary analog input.




Appendix G Glossary of Terms

SCADA – Supervisory Control And Data Acquisition. This term represents any

computing system designed to perform high-level control and monitoring over
various subsystems. On the PowerWizard, we provide a MODBUS interface to
allow any SCADA systems to connect and collect data about the operations of
the control and the generator set(s).

RTU – Remote Transmitter Unit. This term refers to a Slave device in a MODBUS
network, that merely responds to requests from the Master. The PowerWizard
can function as an RTU on a SCADA system.

CRC – Cyclic Redundancy Check. This is an algorithm used to catch transmission
errors. The CRC is generated and transmitted at the source, then re-generated
and compared at the target. The PowerWizard performs a 16-bit CRC check,
which is often called a CRC16 algorithm.

FID – Fault IDentifier. This is a term for a range of data that represents an application-
level fault. For example, this may communicate that the requested operation is
not currently applicable, or that a value requested is out of range.

FMI – Failure Mode Indicator. The J1939 term for a failure code associated with a
particular Suspect Parameter Number. For a complete list of FMI codes, refer to
the Systems Operation Troubleshooting Testing and Adjusting guide.

J1939 – A communication protocol with widespread use in the transportation and power
generation industry. The PowerWizard 1.0 supports a J1939 data link, termed
the Primay Data Link. The PowerWizard 2.0 and 3.0 support the Primary Data
Link, and a second J1939 data link, termed the Accessory Data Link.

NULL character – The name for the ASCII character represented by $00 (1 byte of
binary zeroes). This character is commonly used to mark the termination of an
ASCII string.

SPN – Suspect Parameter Number. The J1939 term for any parameter whose data is
transmitted over a J1939 network, such as the PowerWizard primary or
accessory data link. For a complete list of SPNs supported by the PowerWizard,
refer to the PowerWizard technical manual.

RMS – a mathematical approach of representing a useful “average” for varying
quantities; this is useful to indicate AC quantities.

Page 87

PowerWizard Modbus Manual – DRAFT Version0.8 87


Caterpillar Inc.
Non-Confidential

Similer Documents