Walchem W600 Operating Manual

W600/W900 Modbus

Instruction Manual

WALCHEM, Iwaki America Inc.

Five Boynton Road Hopping Brook Park Holliston, MA 01746 USA : TEL: [phone] WEB: www.walchem.com

Notice

© 2018 WALCHEM, Iwaki America Inc. (hereinafter “Walchem”) 5 Boynton Road, Holliston, MA 01746 USA

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The information and descriptions contained herein are the property of WALCHEM. Such information and descriptions may not be copied or reproduced by any means, or disseminated or distributed without the express prior written permission of WALCHEM, 5 Boynton Road, Holliston, MA 01746.

This document is for information purposes only and is subject to change without notice.

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WALCHEM warrants equipment of its manufacture, and bearing its identification to be free from defects in workmanship and material for a period of 24 months for electronics and 12 months for mechanical parts and electrodes from date of delivery from the factory or authorized distributor under normal use and service and otherwise when such equipment is used in accordance with instructions furnished by WALCHEM and for the purposes disclosed in writing at the time of purchase, if any. WALCHEM’s liability under this warranty shall be limited to replacement or repair, F.O.B. Holliston, MA U.S.A. of any defective equipment or part which, having been returned to WALCHEM, transportation charges prepaid, has been inspected and determined by WALCHEM to be defective. Replaceable elastomeric parts and glass components are expendable and are not covered by any warranty.

THIS WARRANTY IS IN LIEU OF ANY OTHER WARRANTY, EITHER EXPRESS OR IMPLIED, AS TO DESCRIPTION, QUALITY, MERCHANTABILITY, FITNESS FOR ANY PARTICULAR PURPOSE OR USE, OR ANY OTHER MATTER.

180676 Rev F

October 2018

Table of Contents

1.0	SCOPE		...............................................................................................................................................................	1
2.0	INTRODUCTION ................................................................................................................................................			1
3.0	OVERVIEW........................................................................................................................................................			1
3.1		Modbus .....................................................................................................................................................................Settings		2
4.0	MODBUS/TCP ......................................................................................................................................DRIVER			2
4.1		Modbus/TCP ............................................................................................................................................................Protocol		2
	4.1.1	MBAP ....................................................................................................................................................................Header		2
	4.1.2	Protocol .............................................................................................................................................................Data Unit		3
	4.1.3	Modbus/TCP ............................................................................................................................................Function Codes		3
	4.1.3.1 .....................................................................................................................................		Function Code 1, Read Coils	4
	4.1.3.2 ....................................................................................................................		Function Code 2, Read Discrete Inputs	4
	4.1.3.3 ................................................................................................................		Function Code 3, Read Holding Registers	5
	4.1.3.4 ....................................................................................................................		Function Code 4, Read Input Registers	5
	4.1.3.5 ...........................................................................................................................		Function Code 5, Write Single Coil	6
	4.1.3.6 ......................................................................................................		Function Code 6, Write Single Holding Register	6
	4.1.3.7 ...............................................................................................		Function Code 16, Write Multiple Holding Registers	7
	4.1.4 Modbus/TCP ..................................................................................................................................Exception Error Codes			7
4.2		TCP/IP ......................................................................................................................................................................Interface		8
4.3		Data ...........................................................................................................................................................................Refresh		8
4.4		Data ........................................................................................................................................................................Encoding		8
	4.4.1 Coils ...................................................................................................................................................and Discrete Inputs			8
	4.4.1.1 ....................................................................................................................................................................		Boolean	8
	4.4.2 Holding .................................................................................................................................Register and Input Registers			8
	4.4.2.1 .............................................................................................................................................		16 - Bit Word (Boolean)	8
	4.4.2.2 ...............................................................................................................................................		16 - Bit Word (Bitfield)	9
	4.4.2.3 ................................................................................................................................................		16 - Bit Word (Status)	9
	4.4.2.4 ...............................................................................................................................................		16 - Bit Word (Integer)	9
	4.4.2.5 ...............................................................................................................................................		32 - Bit Value (Integer)	9
	4.4.2.6 ..................................................................................................................................................		32 - Bit Value (Float)	9
	4.4.2.7 ........................................................................................................		32 - Bit Inverse Data Format (Integer or Float)	10
5.0	DATA DICTIONARY..........................................................................................................................................			10
5.1		Addressing ...................................................................................................................................................(0- or 1-Based)		10
5.2		Address .......................................................................................................................................................................Maps		10
	5.2.1 W600 ................................................................................................................Controller – I/O Channel Address Maps			11
	5.2.2 W900 ................................................................................................................Controller – I/O Channel Address Maps			12
	5.2.3	Alternate ..................................................................................................................................................Address Maps		14
5.3		Type ..................................................................................................................................................-Specific Address Map		15
	5.3.1	System .......................................................................................................................................................Address Map		15
	5.3.2	Network .....................................................................................................................................................Address Map		16
	5.3.3 Sensor .............................................................................................................................................Input Address Maps			17
	5.3.3.1 .................................................................		Sensor Input (all types except Analog Input Flowmeter) Address Map	17
	5.3.3.2 ..................................................................................................................		Analog Input Flowmeter Address Map	18
	5.3.4 Digital ..............................................................................................................................................Input Address Maps			19
	5.3.4.1 .............................................................................................................		Digital Input / DI State Type Address Map	19
	5.3.4.2 .....................................................................................		Digital Input / Contacting Flow Meter Type Address Map	20
	5.3.4.3 .................................................................................		Digital Input / Paddlewheel Flow Meter Type Address Map	21
	5.3.4.4 ........................................................................................................		Digital Input / DI Counter Type Address Map	22
	5.3.4.5 ....................................................................................................		Digital Input / Flow Monitor Type Address Map	23
	5.3.5 Virtual .............................................................................................................................................Input Address Maps			24
	5.3.5.1 ..................................................................................		Virtual Input / Calculation & Raw Value Type Address Map	24

5.3.5.2		Virtual Input / Redundant Sensor Type Address Map ...........................................................................................	25
5.3.5.3		Virtual Input / Disturbance Type Address Map .....................................................................................................	26
5.3.6 Relay Output Address Maps ............................................................................................................................................			27
5.3.6.1		Relay Output / Manual Control Mode Address Map .............................................................................................	27
5.3.6.2		Relay Output / On/Off & On/Off Disturbance Control Mode Address Map ..........................................................	28
5.3.6.3		Relay Output / Dual Setpoint Control Mode Address Map....................................................................................	29
5.3.6.4		Relay Output / Time Proportional Control Mode Address Map ............................................................................	30
5.3.6.5		Relay Output / Intermittent Sampling Control Mode Address Map......................................................................	31
5.3.6.6		Relay Output / Bleed And Feed Control Mode Address Map ................................................................................	32
5.3.6.7		Relay Output / Bleed Then Feed Control Mode Address Map...............................................................................	33
5.3.6.8		Relay Output / Flow Timer Control Mode Address Map .......................................................................................	34
5.3.6.9		Relay Output / Counter Timer Control Mode Address Map ..................................................................................	35
5.3.6.10		Relay Output / Target PPM Control Mode Address Map.......................................................................................	36
5.3.6.11		Relay Output / PPM By Volume Control Mode Address Map................................................................................	37
5.3.6.12		Relay Output / Flow Meter Ratio Control Mode Address Map..............................................................................	38
5.3.6.13		Relay Output / Volumetric Blend Control Mode Address Map..............................................................................	39
5.3.6.14		Relay Output / Percent Timer Control Mode Address Map...................................................................................	40
5.3.6.15		Relay Output / Event Timer Control Mode Address Map ......................................................................................	41
5.3.6.16		Relay Output / Biocide Timer Control Mode Address Map ...................................................................................	42
5.3.6.17 Relay Output / Spike Control Mode Address Map.................................................................................................			43
5.3.6.18 Relay Output / Probe Wash Control Mode Address Map......................................................................................			44
5.3.6.19 Relay Output / Plating Control Mode Address Map ..............................................................................................			45
5.3.6.20 Relay Output / Plating Follow Control Mode Address Map...................................................................................			46
5.3.6.21 Relay Output / Lag Output Control Mode Address Map........................................................................................			47
5.3.6.22 Relay Output / Alarm Control Mode Address Map................................................................................................			48
5.3.7 Pulse Relay Output Address Maps...................................................................................................................................			49
5.3.7.1		Pulse Relay Output / Manual Control Mode Address Map....................................................................................	49
5.3.7.2		Pulse Relay Output / Pulse Proportional Control Mode Address Map ..................................................................	50
5.3.7.3		Pulse Relay Output / Flow Proportional Control Mode Address Map ...................................................................	51
5.3.7.4		Pulse Relay Output / Pulse PID Control Mode Address Map .................................................................................	52
5.3.7.5		Pulse Relay Output / Pulse Disturbance Control Mode Address Map ...................................................................	53
5.3.7.6		Pulse Relay Output / Lag Output Control Mode Address Map ..............................................................................	54
5.3.8 Analog Output Address Maps..........................................................................................................................................			55
5.3.8.1		Analog Output / Manual Control Mode Address Map...........................................................................................	55
5.3.8.2		Analog Output / Retransmit Mode Address Map ..................................................................................................	56
5.3.8.3		Analog Output / Proportional Control Mode Address Map...................................................................................	57
5.3.8.4		Analog Output / Flow Proportional Control Mode Address Map ..........................................................................	58
5.3.8.5		Analog Output / PID Control Mode Address Map .................................................................................................	59
5.3.8.6		Analog Output / Disturbance Control Mode Address Map....................................................................................	60
5.3.8.7		Analog Output / Lag Output Control Mode Address Map .....................................................................................	61
5.3.9	Alternate Address Maps ..................................................................................................................................................		62
5.3.9.1		Alternate Sensor Input Address Map.....................................................................................................................	62
5.3.9.2		Alternate Digital Input Address Map .....................................................................................................................	63
5.3.9.3		Alternate Virtual Input Address Map.....................................................................................................................	64
5.3.9.4		Alternate Relay Output Address Map....................................................................................................................	65
5.3.9.5		Alternate Analog Output Address Map .................................................................................................................	66
5.3.9.6		Alternate Control Output Address Map.................................................................................................................	67
5.4	Status Register Codes...........................................................................................................................................................		68
5.5	Alarm Bitfields......................................................................................................................................................................		70
5.5.1	System Alarm Bitfield ......................................................................................................................................................		70
5.5.2	Network Alarm Bitfield....................................................................................................................................................		70
5.5.3 Sensor Input Alarm Bitfield .............................................................................................................................................			71
5.5.4 Digital Input Alarm Bitfield ..............................................................................................................................................			71
5.5.5 Virtual Input Alarm Bitfield..............................................................................................................................................			72
5.5.6 Relay & Control Output Alarm Bitfield ............................................................................................................................			72
5.5.7 Analog Output Alarm Bitfield ..........................................................................................................................................			73

1.0 SCOPE

This document is a User Interface Specification for the Walchem Modbus/TCP product feature for W600 and W900 Controllers. It contains mapping of the various dynamic variables to their Modbus/TCP address locations.

This document supports the Modbus/TCP feature on controller software versions 3.01 and higher.

2.0 INTRODUCTION

The Modbus/TCP feature allows the Walchem controller to communicate with PC-based applications such as WonderWare and Intellution HMI/SCADA programs, Building Energy Management systems, Distributed Control Systems (DCS), as well as stand-alone HMI devices.

The controller is a Modbus Server, meaning that it can respond to requests from the HMI device. The controller cannot initiate the flow of information. For example, it will not immediately send a new alarm message. It will wait until the HMI device requests the current data contained in specific address locations.

If the HMI device does not directly support the Modbus/TCP protocol, then a protocol translation gateway may be required to convert from Modbus/TCP to a protocol that the device supports. Please note that Modbus/RTU requires a serial interface, not Ethernet, and therefore is not directly compatible with the Walchem controller.

3.0 OVERVIEW

Modbus/TCP, also known as Modbus TCP/IP, is a form of Modbus that uses the TCP/IP layers as a base for controlling the communications between different devices. This is not to be confused with Modbus over TCP/IP, which Walchem controllers do not support.

The Modbus/TCP protocol supports multiple types of data transactions, from reading single bits per transaction, to advanced object-oriented operations. However, to ensure the most compatible system available, only a basic subset of these functions is supported in the controller.

The official Modbus/TCP protocol supports data addresses 5 digits in length. A de facto extended standard exists which supports data addresses 6 digits in length. However, to ensure compatibility, the Modbus/TCP feature supports only 5-digit data address system.

The Modbus/TCP feature supports reading and writing of single-bit Coils and 16-bit Holding Registers, as well as read-only single-bit Discrete Inputs and 16-bit Input Registers. These data formats allow the controller to establish blocks that contain all the process variables, set points, alarms, and input/output status values that are made public to a Modbus/TCP client. These blocks of data are packaged so that it can be read in 8-bit chunks (for a group of up to 8 Coils or Discrete Inputs) or 16-bit chunks (for a single Holding Register or Input Register), regardless of the type of data within it. In the following sections, the formatting, storing, and reading of this data are described.

1

3.1Modbus Settings

Settings relating to the Modbus/TCP feature can be configured in the Remote Communication Configuration Menu.

The ‘Verbose Logging’ setting is used to generate an Event log entry for every Modbus message into and out of the controller. The information may be used in conjunction with an HMI log when troubleshooting communications during commissioning. However, the additional logging adds a significant load on the controller’s systems. Therefore, this feature should only be enabled temporarily while actively troubleshooting communications. The setting automatically reverts to Disabled when the controller is restarted.

Detailed information on the Remote Communication Configuration Menu can be found in the controller Instruction Manual.

4.0MODBUS/TCP DRIVER

4.1Modbus/TCP Protocol

The Modbus protocol, as well as the Modbus/TCP variant, is well documented in the specifications which are available at http://www.modbus.org, a website established by the Modbus Organization for supporting and organizing the Modbus protocol.

The Modbus/TCP Application Data Unit (ADU) consists of 2 distinct sections:

	Modbus Application Protocol (MBAP)				Protocol Data Unit (PDU)
	Header

The total size of the ADU is between 9 and 263 bytes, depending on the function code and number of data addresses requested.

4.1.1 MBAP Header

The Modbus/TCP extension adds 7 additional bytes to the original Modbus protocol, which allows for the transport over the TCP/IP layers. These 7 bytes make up the MBAP Header:

Modbus Application Protocol (MBAP) Header

	Name		Size	Description
	Transaction Identifier		2 bytes	Identification of Request/Response transaction.
				Copied from request to response
	Protocol Identifier		2 bytes	0 = Modbus protocol.
	Length		2 bytes	Number of following bytes (includes the Unit Identifier and PDU)
	Unit Identifier		1 byte	Identification of Remote Device.
				Can be used for broadcasting (unsupported).

The Unit Identifier has a special consideration in the Modbus/TCP implementation. If the value is 0, then the request is a broadcast message and the packet will be processed, but no response will be generated. If the value is non-zero, the packet will be processed and a response will be returned.

Normally the Slave ID, which is not present in the Modbus/TCP protocol, will be set in the HMI client software to 1. The broadcast Unit Identifier address is not supported by the controller; all supported function codes require a response message at all times.

2

4.1.2 Protocol Data Unit

The Protocol Data Unit (PDU) is made up of between 2 and 256 bytes, depending on the function and number of data addresses requested:

				Protocol Data Unit (PDU)
	Name		Size	Description
	Function Code		1 byte	Function Code identifier.
				Can be any of the hexadecimal codes listed in the Function Code table.
	Data Payload		1 – 255	Payload for request/response transactions.
			byte(s)	Varies depending on function code and number of addresses requested.

4.1.3 Modbus/TCP Function Codes

The Modbus/TCP Server feature supports the following function codes:

							Supported Function Codes
	Function			Name			Description			Data Address
	Code									Range
	FC1			Read Coils			Read up to 2000 consecutive 1-bit Coils within a single			0xxxx
	(0x01)						request/response cycle.
	FC2			Read Discrete			Read up to 2000 consecutive 1-bit Discrete Inputs			1xxxx
	(0x02)			Inputs			within a single request/response cycle.
	FC3			Read Holding			Read up to 125 consecutive 16-bit Holding Registers			4xxxx
	(0x03)			Registers			within a single request/response cycle.
	FC4			Read Input			Read up to 125 consecutive 16-bit Input Registers			3xxxx
	(0x04)			Registers			within a single request/response cycle.
	FC5			Write Single Coil			Write a single 1-bit Coil within a single			0xxxx
	(0x05)						request/response cycle.
	FC6			Write Single			Write a single 16-bit Holding Register within a single			4xxxx
	(0x06)			Holding Register			request/response cycle.
	FC16			Write Multiple			Write up to 125 consecutive 16-bit Holding Registers			4xxxx
	(0x10)			Holding Registers			within a single request/response cycle.

The consecutive address limitations of the Coils, Discrete Inputs, Holding Registers, and Input Registers were established for the Modbus/TCP standard to maintain consistency with the original Modbus protocol standard, even though a TCP/IP packet can contain a larger payload.

The Modbus/TCP feature allows for Function Codes 1 and 2 to be used interchangeably for read requests. For example, a read coils (FC1) request for data addresses 00605 through 00610 will always return the same result as a read discrete inputs (FC2) request for data addresses 10605 through 10610.

Likewise, the Modbus/TCP feature allows for Function Codes 3 and 4 to also be used interchangeably for read requests. For example, a read holding registers (FC3) request for data addresses 40587 through 40590 will always return the same result as a read input registers (FC4) request for data addresses 30587 through 30590. All addresses accessible as a Coil or Discrete Input may also be accessed as a Holding Register or Input Register.

Only the 4 least significant digits of the data address are explicitly stated in the Modbus message, with the most significant (5th) digit being derived from the function code. However, generally the entire 5-digit data address must be specified in the Tag Database of an HMI.

3

4.1.3.1 Function Code 1, Read Coils

		Read Coils Request PDU
Name	Size	Description
Function Code	1 Byte	Function Code Identifier (0x01).
Starting Address	2 Bytes	The data address of the first Coil to read.
Quantity of Coils	2 Bytes	The number of Coils requested, maximum of 2000 per message.

		Read Coils Response PDU
Name	Size	Description
Function Code	1 Byte	Function Code Identifier (0x01).
	1 Byte	The number of data bytes to follow.
Byte Count
Coil Status	1-125 Bytes	8 Coils per byte, up to 2000 Coils per message.

		Read Coils Exception PDU
Name	Size	Description
	1 Byte	0x80 plus Function Code Identifier (0x81).
Error Code
	1 Byte	See 4.1.4 Modbus/TCP Exception Error Codes
Exception Code

4.1.3.2 Function Code 2, Read Discrete Inputs

				Read Discrete Inputs Request PDU
	Name		Size		Description
	Function Code		1 Byte		Function Code Identifier (0x02).
			2 Bytes		The data address of the first Discrete Input to read.
	Starting Address
					The number of Discrete Inputs requested, maximum of 2000 per
	Quantity of		2 Bytes
	Discrete Inputs				message.

					Read Discrete Inputs Response PDU
	Name			Size			Description
				1 Byte			Function Code Identifier (0x02).
	Function Code
				1 Byte			The number of data bytes to follow.
	Byte Count
	Discrete Input			1-125 Bytes			8 Discrete Inputs per byte, up to 2000 Discrete Inputs per
	Status						message.

		Read Discrete Inputs Exception PDU
Name	Size		Description
Error Code	1 Byte		0x80 plus Function Code Identifier (0x82).
	1 Byte		See 4.1.4 Modbus/TCP Exception Error Codes
Exception Code

4

4.1.3.3 Function Code 3, Read Holding Registers

				Read Holding Registers Request PDU
	Name		Size		Description
	Function Code		1 Byte		Function Code Identifier (0x03).
	Starting Address		2 Bytes		The data address of the first Holding Register to read.
	Quantity of		2 Bytes		The total number of Holding Registers requested, maximum of
	Holding Registers				125 per message.

				Read Holding Registers Response PDU
	Name		Size		Description
	Function Code		1 Byte		Function Code Identifier (0x03).
	Byte Count		1 Byte		The number of data bytes to follow.
	Holding Register		2-250 Bytes		1 Holding Register for every 2 bytes, maximum of 125 Holding
	Values				Registers per message.

		Read Holding Registers Exception PDU
Name	Size		Description
Error Code	1 Byte		0x80 plus Function Code Identifier (0x83).
Exception Code	1 Byte		See 4.1.4 Modbus/TCP Exception Error Codes

4.1.3.4 Function Code 4, Read Input Registers

					Read Input Registers Request PDU
	Name			Size			Description
	Function Code			1 Byte			Function Code Identifier (0x04).
	Starting Address			2 Bytes			The data address of the first Input Register to read.
	Quantity of Input			2 Bytes			The total number of Input Registers requested, maximum of 125
	Registers						per message.

				Read Input Registers Response PDU
	Name		Size		Description
			1 Byte		Function Code Identifier (0x04).
	Function Code
	Byte Count		1 Byte		The number of data bytes to follow.
	Input Register		2-250 Bytes		1 Input Register for every 2 bytes, maximum of 125 Input
	Values				Registers per message.

		Read Input Registers Exception PDU
Name	Size		Description
Error Code	1 Byte		0x80 plus Function Code Identifier (0x84).
Exception Code	1 Byte		See 4.1.4 Modbus/TCP Exception Error Codes

5

4.1.3.5 Function Code 5, Write Single Coil

		Write Single Coil Request PDU
Name	Size		Description
Function Code	1 Byte		Function Code Identifier (0x05).
Coil Address	2 Bytes		The data address of the Coil to which to write.
Coil Value	2 Bytes		The value to write to the Coil (0xFF00 = On, 0x0000 = Off).

		Write Single Coil Response PDU
Name	Size		Description
Function Code	1 Byte		Function Code Identifier (0x05).
	2 Bytes		The data address of the Coil written.
Coil Address
Coil Value	2 Bytes		The value written to the Coil (0xFF00 = On, 0x0000 = Off).

		Write Single Coil Exception PDU
Name	Size		Description
	1 Byte		0x80 plus Function Code Identifier (0x85).
Error Code
	1 Byte		See 4.1.4 Modbus/TCP Exception Error Codes
Exception Code

4.1.3.6 Function Code 6, Write Single Holding Register

Write Single Holding Register Request PDU

	Name		Size	Description
	Function Code		1 Byte	Function Code Identifier (0x06).
	Holding Register		2 Bytes	The data address of the Holding Register to which to write.
	Address
	Holding Register		2 Bytes	The value to write to the Holding Register.
	Value

Write Single Holding Register Response PDU

	Name		Size	Description
	Function Code		1 Byte	Function Code Identifier (0x06).
	Holding Register		2 Bytes	The data address of the Holding Register written.
	Address
	Holding Register		2 Bytes	The value written to the Holding Register.
	Value

Write Single Holding Register Exception PDU

Name	Size	Description
Error Code	1 Byte	0x80 plus Function Code Identifier (0x86).
Exception Code	1 Byte	See 4.1.4 Modbus/TCP Exception Error Codes

6

4.1.3.7 Function Code 16, Write Multiple Holding Registers

Write Multiple Holding Registers Request PDU

	Name		Size	Description
	Function Code		1 Byte	Function Code Identifier (0x10).
	Starting Address		2 Bytes	The data address of the first Holding Register to which to write.
	Quantity of		2 Bytes	Number of Holding Registers to write.
	Holding Registers
	Byte Count		1 Byte	The number of data bytes to follow.
	Holding Register		1-250 Bytes	2 bytes for every Holding Register, maximum of 125 Holding
	Values			Registers per message.

Write Multiple Holding Registers Response PDU

	Name		Size	Description
	Function Code		1 Byte	Function Code Identifier (0x10).
	Starting Address		2 Bytes	The data address of the Holding Register written.
	Quantity of		2 Bytes	Number of Holding Registers written.
	Holding Registers

Write Multiple Holding Registers Exception PDU

Name	Size	Description
Error Code	1 Byte	0x80 plus Function Code Identifier (0x90).
Exception Code	1 Byte	See 4.1.4 Modbus/TCP Exception Error Codes

4.1.4 Modbus/TCP Exception Error Codes

The Modbus/TCP feature supports the following Exception (Error) Codes:

			Supported Exception Codes
	Exception Code		Name	Description
	0x01		Illegal Function	The function code received is not supported in the
				controller.
				The data address received is not an allowable address within
	0x02		Illegal Data Address	the controller. This error will only be generated if the first
				register requested is not valid for the function.
				A value contained in the query data field for a Write
	0x03		Illegal Data Value	command is not an allowable value for field. This error will
				only be generated if the first register requested is not valid
				for the function.
				An unrecoverable error occurred while the controller was
	0x04		Slave Device Failure	attempting to perform the requested action. This is a
				general exception code indicating that the request was valid,
				but the controller could provide a response.

When an exception occurs, the Response PDU contains a Function Code of 0x80 plus the original hexadecimal Function Code.

7

4.2TCP/IP Interface

The Modbus/TCP interface is attached to the TCP/IP stack that is implemented within the Walchem controller. When the Modbus feature is Enabled, the controller will listen to all communications that come in on the Modbus/TCP registered port 502. This port can be changed in the Remote Communications Menu.

4.3Data Refresh

To ensure continued connectivity, the Modbus/TCP client should not request data more frequently than once every 5000 msec. Faster refresh rates are unsupported and may result in unexpected behavior.

4.4Data Encoding

Modbus uses a ‘big-endian’ representation for addresses and data items. This means that within each register, when a numerical quantity larger than a single byte is transmitted, the MOST significant byte is sent first. The following topics describe the different types of encoding and show how the data is encoded within the Modbus/TCP packet. Most client drivers will extract the data from the packet in the correct format for use/display within the client environment.

4.4.1 Coils and Discrete Inputs

4.4.1.1 Boolean

Coils and Discrete Inputs can be used for digital input states, relay states, alarm states, and reset buttons that are representable as a 1 or a 0. All binary data is packed from least significant bit to most significant bit into a byte containing up to 8 Coils or Discrete Inputs. Bits not containing the value of a Coil or Discrete Input are space holders and have a value of 0.

	Byte Value	Coil 1	Coil 2	6 unused bits
	0x02	0	1	000000
	(00000010)

Reset buttons may also be packed as a 16-bit word when using the Write Single Coil function code. (0xFF00 = On, 0x0000 = Off)

	Word Value	Coil Value	Most Significant Byte	Least Significant Byte
	0xFF00	1	0xFF	0x00
	(1111111100000000)		(11111111)	(00000000)

4.4.2 Holding Register and Input Registers

4.4.2.1 16-Bit Word (Boolean)

Holding Registers and Input Registers can be used for digital input states, relay states, alarm states, and reset buttons that are representable as a 1 or a 0. All binary data can be packed into a 16-Bit register, with the least significant bit of the least significant byte being occupied by the 1-bit value. This is functionally identical to a 16-bit integer.

Word Value	Bit Value		Most Significant Byte		Least Significant Byte
0x0001	1		0x00		0x01
(0000000000000001)			(00000000)		(00000001)

8

4.4.2.2 16-Bit Word (Bitfield)

Holding Registers and Input Registers can be used for Alarm Bitfields. An 8-Bit Alarm bitfield is packed into the least significant byte of a 16-bit register. This is offered as a single-register alternative to accessing alarm states individually. Bitfields can be decoded in section 5.5 Alarm Bitfields.

Word Value		Alarm Bitfield Value	Most Significant Byte		Least Significant Byte
0x00AA		0xAA	0x00		0xAA
(0000000010101010)			(00000000)		(10101010)

4.4.2.3 16-Bit Word (Status)

Holding Registers and Input Registers can be used for enumerated values such as status codes. An 8-Bit status code is packed into the least significant byte of a 16-bit register. This is functionally identical to the 16-bit integer. Status codes are defined in section 5.4 Status Register Codes.

	Word Value	Alarm Bitfield Value	Most Significant Byte	Least Significant Byte
	0x00AA	0xAA	0x00	0xAA
	(0000000010101010)		(00000000)	(10101010)

4.4.2.4 16-Bit Word (Integer)

Holding Registers and Input Registers can be used for 16-bit integers containing HOA settings, and time data that don’t require 32-bit integers. All 16-bit integers are unsigned.

Word Value	Most Significant Byte	Least Significant Byte
0x1234	0x12	0x34

4.4.2.5 32-Bit Value (Integer)

Holding Registers and Input Registers can be used for 32-bit integer data containing elapsed time values and timestamps. The system clock register and all registers containing timestamps use the Unix Time format, that counts the seconds passed since 12:00:00 am, January 1st, 1970. Registers are only 16 bits wide; therefore, a request message must include 2 consecutive registers to read or write a 32-bit integer. The 32-bit value is transmitted with the least significant word first, then the most significant word. All 32-bit integers are unsigned.

	Word Value		Register 1		Register 2
			Most Significant	Least Significant	Most Significant	Least Significant
			Least Significant Word		Most Significant Word
	0x12345678		0x56	0x78	0x12	0x34

4.4.2.6 32-Bit Value (Float)

Holding Registers and Input Registers can be used for 32-bit floating point data containing set points, sensor readings, percentages, deadbands, etc. Registers are only 16 bits wide; therefore, a request message must include 2 consecutive registers to read or write a 32-bit float. The 32-bit value is transmitted with the least significant word first, then the most significant word.

	Word Value		Register 1		Register 2
			Most Significant	Least Significant	Most Significant	Least Significant
			Least Significant Word		Most Significant Word
	0x12345678		0x56	0x78	0x12	0x34
				9

4.4.2.7 32-Bit Inverse Data Format (Integer or Float)

32-bit integers and floats can use an inverse data format, where the contents of registers 1 and 2 are switched. When inverse data format is selected, the 32-bit value is transmitted with the most significant word first, then the least significant word. The data format setting can be modified in the Remote Communications Settings Menu.

			Register 1		Register 2
	Word Value		Most Significant	Least Significant	Most Significant	Least Significant
			Most Significant Word		Least Significant Word
	0x12345678		0x12	0x34	0x56	0x78

5.0DATA DICTIONARY

5.1Addressing (0- or 1-Based)

The addressing within the Modbus/TCP protocol (that is, the data within the physical packet) is 0-based, meaning the first element/item to be accessed is referenced by address 0. The Modbus standard for handling and displaying data is 1-based, meaning the first element/data item to be accessed is referenced by address 1.

For most client applications, users enter the 1-based number which is converted to 0-based addressing at the protocol level. The addresses defined in the following address maps below are 1-based, as most of the client applications work with this method. Register addresses for individual elements are derived by adding the address offset in the appropriate Type-Specific Address Map to the starting address in the I/O Channel Address Map below.

5.2Address Maps

The address map is a function code-agnostic map that contains all data values that can be accessed as Coils (0xxxx), Discrete Inputs (1xxxx), Holding Registers (4xxxx), and Input Registers (3xxxx).

The Address Map of the Modbus/TCP feature is modular; valid addresses are determined by the add-on card configuration of the controller and the task being performed by each Input or Output. Each object has a block of 36 addresses.

The Modbus/TCP feature allows all addresses to be accessed as registers. On the following address map tables, values in BOLD can also be accessed as a Coil or Discrete Input.

As examples, to read the ‘Controller Firmware Version’ from the System Address Map (starting address x0037) as an Input Register (FC4), the address indices 2 and 3 must be requested together: Addresses 30039 and 30040.

To read the ‘Low Alarm’ status for Sensor 2-1 in a W600 Controller as a Coil (FC1), the Sensor Input Address Map indicates the starting address is x0865. Address index 28 must be requested: Address 00893. For the W900 Controller, the ‘Low Alarm’ status for Sensor 2-1 is x1729 + 28 = Address 01757.

To write the ‘Setpoint’ for Relay 3 (set to On/Off control mode) in the Relay On/Off Control Mode Address Map (staring address x9001) as a Holding Register (FC6), the address indices 6 and 7 must be used together: Addresses 49007 and 49008.

10

5.2.1 W600 Controller – I/O Channel Address Maps

The address ranges for each input/output channel in the W600 controller are as follows:

W600 Controller – I/O Channel Address Map

	Object			Starting			Ending			Type-Specific Address Maps
				Address			Address
	System			x0037			x0072			See 5.3.1 System Address Map
	Network			x0145			x0180			See 5.3.2 Network Address Map
	Sensor Input 1-1			x0577			x0612
	Sensor Input 1-2			x0613			x0648
	Sensor Input 1-3			x0649			x0684			See 5.3.3 Sensor Input Address Maps
	Sensor Input 2-1			x0865			x0900
	Sensor Input 2-2			x0901			x0936
	Sensor Input 2-3			x0937			x0972
	Digital Input 1			x0289			x0324
	Digital Input 2			x0325			x0360
	Digital Input 3			x0361			x0396			See 5.3.4 Digital Input Address Maps
	Digital Input 4			x0397			x0432
	Digital Input 5			x0433			x0468
	Digital Input 6			x0469			x0504
	Virtual Input 1			x5761			x5796			See 5.3.5 Virtual Input Address Maps
	Virtual Input 2			x5797			x5832
	Relay Output 1			x8929			x8964
	Relay Output 2			x8965			x9000			See 5.3.6 Relay Output Address Maps
	Relay Output 3			x9001			x9036			Or
	Relay Output 4			x9037			x9072
	Relay Output 5			x9073			x9108			5.3.7 Pulse Relay Output Address Maps
	Relay Output 6			x9109			x9144
	Analog Output 1			x1153			x1188			See 5.3.8 Analog Output Address Maps
	Analog Output 2			x1189			x1224

11

5.2.2 W900 Controller – I/O Channel Address Maps

The address ranges for each input/output channel in the W900 controller are as follows:

W900 Controller – I/O Channel Address Map

	Object			Starting Address		Ending Address			Type-Specific Address Maps
	System			x0037		x0072		See 5.3.1 System Address Map
	Network			x0145		x0180		See 5.3.2 Network Address Map
	Sensor Input 1-1			x1153		x1188
	Sensor Input 1-2			x1189		x1224
	Sensor Input 1-3			x1225		x1260
	Sensor Input 1-4			x1261		x1296
	Sensor Input 1-5			x1297		x1332		See 5.3.3 Sensor Input Address Maps
	Sensor Input 1-6			x1333		x1368
	Sensor Input 2-1			x1729		x1764
	Sensor Input 2-2			x1765		x1800		Note: When using P/N 191918 I/O card with
	Sensor Input 2-3			x1801		x1836
	Sensor Input 2-4			x1837		x1872		2 Analog Input + 4 Analog Output channels,
								the two (4-20 mA) Sensor Inputs are mapped
	Sensor Input 2-5			x1873		x1908
								from channels 1 and 2 into channels 5 and 6.
	Sensor Input 2-6			x1909		x1944
	Sensor Input 3-1			x2305		x2340		For example, if the card is installed in the third
	Sensor Input 3-2			x2341		x2376		I/O slot, the register address mapping is:
	Sensor Input 3-3			x2377		x2412		Analog Output 3-1: x2305 to x2340
	Sensor Input 3-4			x2413		x2448
								Analog Output 3-2: x2341 to x2376
	Sensor Input 3-5			x2449		x2484		Analog Output 3-3: x2377 to x2412
	Sensor Input 3-6			x2485		x2520		Analog Output 3-4: x2413 to x2448
	Sensor Input 4-1			x2881		x2916		Sensor Input 3-1:		x2449 to x2484
								Sensor Input 3-2:		x2485 to x2520
	Sensor Input 4-2			x2917		x2952
	Sensor Input 4-3			x2953		x2988
	Sensor Input 4-4			x2989		x3024
	Sensor Input 4-5			x3025		x3060
	Sensor Input 4-6			x3061		x3096
	Digital Input 1			x0577		x0612
	Digital Input 2			x0613		x0648
	Digital Input 3			x0649		x0684
	Digital Input 4			x0685		x0720
	Digital Input 5			x0721		x0756
	Digital Input 6			x0757		x0792		See 5.3.4 Digital Input Address Maps
	Digital Input 7			x0793		x0828
	Digital Input 8			x0829		x0864
	Digital Input 9			x0865		x0900
	Digital Input 10			x0901		x0936
	Digital Input 11			x0937		x0972
	Digital Input 12			x0973		x1008

12

W900 Controller – I/O Channel Address Map

	Object			Starting Address		Ending Address			Type-Specific Address Maps
	Virtual Input 1			x5761		x5796
	Virtual Input 2			x5797		x5832
	Virtual Input 3			x5833		x5868
	Virtual Input 4			x5869		x5904		See 5.3.5 Virtual Input Address Maps
	Virtual Input 5			x5905		x5940
	Virtual Input 6			x5941		x5976
	Virtual Input 7			x5977		x6012
	Virtual Input 8			x6013		x6048
	Relay Output 1			x8929		x8964
	Relay Output 2			x8965		x9000
	Relay Output 3			x9001		x9036		See 5.3.6 Relay Output Address Maps
	Relay Output 4			x9037		x9072			Or
	Relay Output 5			x9073		x9108
	Relay Output 6			x9109		x9144		5.3.7 Pulse Relay Output Address Maps
	Relay Output 7			x9145		x9180
	Relay Output 8			x9181		x9144
	Analog Output 1-1			x1153		x1188
	Analog Output 1-2			x1189		x1224
	Analog Output 1-3			x1225		x1260
	Analog Output 1-4			x1261		x1296
	Analog Output 2-1			x1729		x1764
	Analog Output 2-2			x1765		x1800
	Analog Output 2-3			x1801		x1836
	Analog Output 2-4			x1837		x1872		See 5.3.8 Analog Output Address Maps
	Analog Output 3-1			x2305		x2340
	Analog Output 3-2			x2341		x2376
	Analog Output 3-3			x2377		x2412
	Analog Output 3-4			x2413		x2448
	Analog Output 4-1			x2881		x2916
	Analog Output 4-2			x2917		x2952
	Analog Output 4-3			x2953		x2988
	Analog Output 4-4			x2989		x3024
	Control Output 1			x6913		x6948		See 5.3.6 Relay Output Address Maps
	Control Output 2			x6949		x6984
	Control Output 3			x6985		x7020			Or
	Control Output 4			x7021		x7056		5.3.7 Pulse Relay Output Address Maps
	Control Output 5			x7057		x7092
	Control Output 6			x7093		x7128		Note: Control Outputs share address maps
	Control Output 7			x7129		x7164
								and alarm bitfields with Relay control modes
	Control Output 8			x7165		x7200
					13

5.2.3 Alternate Address Maps

The I/O Address Maps in the previous sections are based on the hardware position/slot within the controller. Alternate Address Maps use software-based, dynamic addressing to provide a more efficient way to access similar data from different objects. Using these address tables, the same field type is accessible using consecutive addresses. For example, the primary values for all sensors installed in the controller can be accessed in a single Modbus FC4 request/response cycle starting at address 39217.

	I/O Type			Available Objects		Type-Specific Alternate Address Map
				Primary Value; Status
	Sensor Inputs			Alarm Bitfield		See 5.3.9.1 Alternate Sensor Input / Temperature Input /
				Low, High Alarms
						Analog Input Address Map
				LoLo, HiHi Alarms
				Calibration Required
				DI State; Interlock State
				Total Time
	Digital Inputs			Flowrate; Flow Total		See 5.3.9.2 Alternate Digital Input Address Map
				Alarm Bitfield
				Low, High Alarms
	Virtual Inputs			Primary Value; Status		See 5.3.9.3 Alternate Virtual Input Address Map
				Alarm Bitfield
				Relay State
	Relay Outputs			Pulse Output Percent		See 5.3.9.4 Alternate Relay Output Address Map
				Time On; Status
				Alarm Bitfield
				Output Percent
	Analog Outputs			Time On; Status		See 5.3.9.5 Alternate Analog Output Address Map
				Alarm Bitfield
				Output State
	Control Outputs			Output Percent		See 5.3.9.6 Alternate Control Output Address Map
				Time On; Status
				Alarm Bitfield

Note that changing I/O card locations can affect the address used to access individual objects. For example, if a W900 is configured with a Dual SI card in slot 1 and a Dual AI card in slot 3, the alternate address mappings for the primary values are different if a Single SI card is inserted into slot 2:

Scenario #1: I/O Slot 2 Not Populated					Scenario #2: I/O Slot 2 Populated
Channel	Address	Alternate		Address	Channel	Address	Alternate			Address
I/O Slot 1: Dual Sensor Input Card					I/O Slot 1: Dual Sensor Input Card
Sensor Input 1-1	x1153	Sensor 1		x9217	Sensor Input 1-1	x1153	Sensor 1			x9217
Sensor Input 1-2	x1189	Sensor 2		x9219	Sensor Input 1-2	x1189	Sensor 2			x9219
Sensor Input 1-3	x1225	Sensor 3		x9221	Sensor Input 1-3	x1225	Sensor 3			x9221
Sensor Input 1-4	x1261	Sensor 4		x9223	Sensor Input 1-4	x1261	Sensor 4			x9223
I/O Slot 2: Not Populated					I/O Slot 2: Single Sensor Input Card
					Sensor Input 2-1	x1729	Sensor 5			x9225
					Sensor Input 2-2	x1765	Sensor 6			x9227
I/O Slot 3: Dual Analog Input Card					I/O Slot 3: Dual Analog Input Card
Sensor Input 3-1	x2305	Sensor 5		x9225	Sensor Input 3-1	x2305	Sensor 7			x9229
Sensor Input 3-2	x2341	Sensor 6		x9227	Sensor Input 3-2	x2341	Sensor 8			x9231

14

5.3Type-Specific Address Maps

5.3.1 System Address Map

System Address Map

	Address	Name	Data Encoding	Permissions	Value
	0	Controller Time	32-Bit Integer	Read	Unix Time
	1
	2	Controller Firmware	32-Bit Float	Read
	3	Version
	4	Date of Last Data Log	32-Bit Integer	Read	Unix Time
	5
	6	Controller Processor	32-Bit Float	Read	°C
	7	Temperature
	8	Network Card	32-Bit Float	Read	°C
	9	Temperature
	10	Digital Input Card	32-Bit Float	Read	°C
	11	Temperature (W900 Only)
	12	I/O Card 1 Temperature	32-Bit Float	Read	°C
	13
	14	I/O Card 2 Temperature	32-Bit Float	Read	°C
	15
	16	I/O Card 3 Temperature	32-Bit Float	Read	°C
	17	(W900 Only)
	18	I/O Card 4 Temperature	32-Bit Float	Read	°C
	19	(W900 Only)
	20
	21
	22
	23
	24
	25
	26	Battery Power	32-Bit Float	Read	Volt
	27
	28	+3.3 V Supply	32-Bit Float	Read	Volt
	29
	30	+5 V Supply	32-Bit Float	Read	Volt
	31
	32	+12 V Supply	32-Bit Float	Read	Volt
	33	(W900 Only)
	34
	35	Alarm Bitfield	16-Bit Bitfield	Read	See 5.5.1 System Alarm Bitfield

15

5.3.2 Network Address Map

Network Address Map

Address		Name		Data Encoding		Permissions		Value
0		VTouch Last Data Time		32-Bit Integer		Read		Unix Time
1
2		VTouch Last		32-Bit Integer		Read		Unix Time
3		Configuration Time
4		VTouch Refresh Rate		32-Bit Float		Read/Write		1 – 1440 Minutes
5
6		VTouch LiveConnect		16-Bit Status		Read		See 5.4 Status Register Codes
		Status
7
8
9
10
11
12
13
14
15
16
17
18		WiFi Signal Strength		32-Bit Float		Read		-30 – -100 dBm
19		(W900 Only)
20		WiFi RSSI		32-Bit Float		Read		0 – 100%
21		(W900 Only)
22		WiFi Channel		32-Bit Float		Read		1 – 14
23		(W900 Only)
24		WiFi Security		16-Bit Status		Read		See 5.4 Status Register Codes
		(W900 Only)
25		WiFi Status (W900 Only)		16-Bit Status		Read		See 5.4 Status Register Codes
		Begin Temporary		Boolean		Read/Write		Write 1 to Begin Temporary
26		Ad-Hoc Mode Session
								Ad-Hoc Mode Session
		(W900 Only)
27
28		Ad-Hoc Mode Time Limit		32-Bit Float		Read/Write		1 – 1440 minutes
29		(W900 Only)
30
31
32
33
34
35		Alarm Bitfield		16-Bit Bitfield		Read		See 5.5.2 Network Alarm
								Bitfield

16

5.3.3 Sensor Input Address Maps

5.3.3.1 Sensor Input (all types except Analog Input Flowmeter) Address Map

Sensor Input (all types except Analog Input Flowmeter) Address Map

Address		Name		Data Encoding		Permissions			Value
0		Primary Value		32-Bit Float		Read		Sensor Units
1
								Cond:	µS/cm before ATC
2								Active, Cu/Ni:	mV
								4-20 mA Input: mA
		Primary Raw Value		32-Bit Float		Read		Temperature:	Ω
								Corrosion Rate: mpy (Mild Steel)
3								Imbalance:	Corrosion Rate
									Imbalance
4		Last Calibration Date		32-Bit Integer		Read		Unix Time
5
6
7
8
9
10		Deadband		32-Bit Float		Read/Write		Sensor Units
11
12		Smoothing Factor		32-Bit Float		Read/Write			0 – 90%
13
14		LoLo Alarm Setpoint		32-Bit Float		Read/Write		Sensor Units
15
16		Low Alarm Setpoint		32-Bit Float		Read/Write		Sensor Units
17
18		High Alarm Setpoint		32-Bit Float		Read/Write		Sensor Units
19
20		HiHi Alarm Setpoint		32-Bit Float		Read/Write		Sensor Units
21
22
23
24
25
26
27
28		Low Alarm		Boolean		Read		1 = Alarm Active
29		High Alarm		Boolean		Read		1 = Alarm Active
30		LoLo Alarm		Boolean		Read		1 = Alarm Active
31		HiHi Alarm		Boolean		Read		1 = Alarm Active
32		Cal Required		Boolean		Read		1 = Alarm Active
33		Input Failure		Boolean		Read		1 = Alarm Active
34		Status		16-Bit Status		Read		See 5.4 Status Register Codes
35		Alarm Bitfield		16-Bit Bitfield		Read		See 5.5.3 Sensor Input Alarm Bitfield
					17

5.3.3.2 Analog Input Flowmeter Address Map

Analog Input Flowmeter Address Map (W900 Controller Only)

Address		Name		Data Encoding		Permissions		Value
0		Primary Value		32-Bit Float		Read		Flow Units
1								Rate Units
2		Primary Raw Value		32-Bit Float		Read		mA
3
4		Last Calibration Date		32-Bit Integer		Read		Unix Time
5
6		Flow Total		32-Bit Float		Read		Flow Units
7
8		Input Filter		32-Bit Float		Read/Write		mA
9
10		Deadband		32-Bit Float		Read/Write		Flow Units
11								Rate Units
12		Smoothing Factor		32-Bit Float		Read/Write		0 – 90%
13
14		LoLo Alarm Setpoint		32-Bit Float		Read/Write		Flow Units
15								Rate Units
16		Low Alarm Setpoint		32-Bit Float		Read/Write		Flow Units
17								Rate Units
18		High Alarm Setpoint		32-Bit Float		Read/Write		Flow Units
19								Rate Units
20		HiHi Alarm Setpoint		32-Bit Float		Read/Write		Flow Units
21								Rate Units
22
23
24
25		Reset Total Flow		Boolean		Read/Write		Write 1 to Reset Flow Total
26
27
28		Low Alarm		Boolean		Read		1 = Alarm Active
29		High Alarm		Boolean		Read		1 = Alarm Active
30		LoLo Alarm		Boolean		Read		1 = Alarm Active
31		HiHi Alarm		Boolean		Read		1 = Alarm Active
32		Cal Required		Boolean		Read		1 = Alarm Active
33		Input Failure		Boolean		Read		1 = Alarm Active
34		Status		16-Bit Status		Read		See 5.4 Status Register Codes
35		Alarm Bitfield		16-Bit Bitfield		Read		See 5.5.3 Sensor Input Alarm Bitfield

18

5.3.4 Digital Input Address Maps

5.3.4.1 Digital Input / DI State Type Address Map

Digital Input / DI State Type Address Map

Address		Name		Data Encoding		Permissions		Value
0		Last Reset Date		32-Bit Integer		Read		Unix Time
1
2		Total Time		32-Bit Integer		Read		Seconds
3
4		Cycle Time		32-Bit Integer		Read		Seconds
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32		Reset Total Time		Boolean		Read/Write		Write 1 to Reset Time
33		DI State		Boolean		Read		0 = Open, 1 = Closed
34		Interlock State		Boolean		Read		0 = Inactive
								1 = Active Interlock
								See 5.5.4 Digital Input Alarm Bitfield
35		Alarm Bitfield		16-Bit Bitfield		Read		When accessed as a Coil,
								Returns 1 if any alarm is active

19

5.3.4.2 Digital Input / Contacting Flow Meter Type Address Map

Digital Input / Contacting Flow Meter Address Map

	Address			Name			Data			Permissions			Value
							Encoding
0				Last Reset Date			32-Bit Integer			Read			Unix Time
1
2				Total Flow			32-Bit Float			Read			Flow Units
3
4
5
6				Total Flow Alarm			32-Bit Float			Read/Write			0 – 1,000,000,000
7				Setpoint									Flow Units
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32				Reset Total Flow			Boolean			Read/Write			Write 1 to Reset Flow Total
33
34
													See 5.5.4 Digital Input Alarm Bitfield
35				Alarm Bitfield			16-Bit Bitfield			Read			When accessed as a Coil,
													Returns 1 if any alarm is active

20