Siemens FDK:085U0321, HART, FDK:085U0226 Operating Instructions Manual

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SITRANS F

Communication Modules

Add-on modules HART

Operating Instructions • 07/2010

HART add-on module

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 Who should use this document? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.4 Abbreviations and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Device Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3. Product overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Product interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 Mechanical Installation MAG/MASS 6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.2 Mechanical installation MAG/MASS 6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.3 General electrical information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.4 HART electrical connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.5 Current output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.5.1 MAG 5000 C/6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.5.2 MASS 6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.6 Local display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.6.1 Menu item explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.6.2 Sensorprom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5. Device Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6. Dynamic Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6.1 MAG 5000 C/6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6.2 MASS 6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

7. Status Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0

7.1 Device status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.2 Extended device status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7.3 Additional device status (Command 48) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

8. Universal Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

9. Common-Practice Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

10. Device-Specific Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

11. Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

11.1 Volume flow unit codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

11.2 Volume unit codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

11.3 Mass flow unit codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

11.4 Mass unit codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

11.5 Temperature unit codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

11.6 Density unit codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

12. Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

12.1 Sampling rates MAG 5000 C/6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

12.2 Sampling rates MASS 6000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

13. Annex A - Capability Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

14. Annex B - Default Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

15. Annex C - Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

HART add-on module

1.5 References

The Siemens HART interface for use with SITRANS F flow transmitters: MAG 5000 C, MAG 6000 and MASS 6000, revision 2, complies with HART protocol Revision 5.2. This document specifies all the device specific features and documents HART Protocol implementation details (e.g. the Engineering units supported). The functionality of this device is described sufficiently to allow its proper application in a process and its complete support in HART capable Host Applications.

This specification is designed to compliment the operating manuals for MAG 5000 C, MAG 6000 and MASS 6000 flow transmitters by providing a complete, unambiguous description of this Field Device from a HART communication perspective. This operating manual does NOT cover MASS 6000 Ex d, MAG 6000 Industry and MAG 6000 Industry Ex d.

The specification is designed to be a technical reference for HART capable Host Application Developers, System Integrators and knowledgeable End Users. It also provides functional specifications (e.g., commands, enumerations and performance requirements) used during Field Device development, maintenance and testing. This document assumes the reader is familiar with HART Protocol requirements and terminology.

AOM Add-On-Module USMII Concept with flexible plug & play fieldbus modules SensorProm Storing unit for all settings HCF HART communication foundation FSK Frequency Shift Keying physical layer CN Capacitance number; capacitance as a multiple of 5000 pF pF Picofarad (10

-12

Farad); unit of electrical capacitance

PV Primary variable SV Secondary variable TV Tertiary variable QV Quaternary variable

Literature 1 MAG 5000 C/MAG 6000 operating manual Order No FDK-521H0739 Literature 2 MASS 6000 operating manual Order No FDK-521H0991

1.1 Scope

1. Introduction / 2. Device Identification

1.2 Purpose

1.3 Who should use this document?

1.4 Abbreviations and Definitions

1. Introduction

This operating manual covers the specifications of the HART interface for MAG 5000 C, MAG 6000 and MASS 6000.

All HART interfaces are based on the same Firmware and Hardware. Below is a table showing the relations between the flow transmitters and the HART interfaces.

HART interface

FDK:085U0226 FDK:085U0321 Integrated MAG 5000 C X MAG 6000 X MASS 6000 X MAG 6000 Industry* X MAG 6000 Industry (Ex d)* X MASS 6000 Ex d* X

* Not described in this operating manual

Devices with the following Firmware version and up are covered in this operating manual.

Firmware

HART module 2.00 MAG 5000 C 3.03 MAG 6000 3.03 MASS 6000 3.00

2. Device Identification

HART add-on module

3. Product overview

MAG/MASS 6000

All interfaces apply to the following specifications:

Manufacturer Siemens Name: Manufacturer ID 42 (2A hex) code: HART Protocol 5.2 revision: Number of Device MAG = 3 Variables: MASS = 4 Physical layers support: FSK Physical Device Category: Current output Loop powered: No CN 10

Device Type 24 = MAG5/6000 + variants Codes: 25 = MASS 6000

Device Revision:2

This operating manual describes the HART interface for the electromagnetic flowmeter MAG 5000 C, MAG 6000 and the coriolis flowmeter MASS 6000.

The MAG/MASS 6000 series is based on the flexible USM II technology. This includes the AOM (Add-On-Module) that provides digital communications capabilities for the USM II transmitters. This approach gives far more flexibility, and greater long-term protection of your signal converter investment, than is possible with factory standard, off-the shelf signal converter designs. With this easy to use system, providing additional functionality to the already impressive lineup of standard features in your USM II transmitter is as easy as plugging in a small black box. You have total control over

whether

to add anything at all,

what

it will be, and

when

to add it.

MAG/MASS 6000

The MAG 5000 C has a built-in HART interface, and cannot be mounted with new communication modules.

3. Product overview

HART add-on module

4. Product interfaces

4.1 Mechanical Installation MAG 5000 C HART

The MAG 5000 C HART is delivered with a build-in HART interface. It is not possible to add additional modules to the MAG 5000 C.

Before proceeding, please make sure that you have the right HART Add-on module. The correct module for MAG 6000 and MASS 6000 is FDK:085U0226. The order number is located on the label of the module.

The installation procedure for the HART module is as follows:

4.2 Mechanical Installation MAG/MASS 6000

4. Product interfaces

1. Unpack the add-on module and insert it in the bottom of the signal converter as shown.

19” rack mounted versions IP 67 compact versions

This completes the add-on module installation, and the signal converter may now be connected to the terminal box. Communication with the display/ keypad and the electrical input/output terminals is established automatically when the power is applied.

2. Press the add-on module in the

direction shown, until it stops and is firmly seated in position.

HART add-on module

4.3 General electrical information

4.4 HART electrical connections

On the electrical termination boards for USM II transmitters, additional input/output terminals have been reserved for add-on module functions. The numbering range of these terminals is as follows, but how many are actually used depends on the type of add-on module. Please refer to the relevant handbook for other electrical connection information.

Terminals reserved for add-on modules:

MAG 5000 C: . . . . . . .91 - 97

MAG 6000: . . . . . . . . .91 - 97

MASS 6000: . . . . . . . .91 - 100

Note

If the MASS 6000 is installed with extra outputs, i.e. have 3 current outputs, 2 digital outputs and 2 relay outputs, then it is not possible to install a HART interface. This is because the extra outputs takes up all terminals.

The following table shows the connection layout for the USM II HART module:

In order to have the HART FSK signal combined with the Current output, two connections must be made. Terminal 31 must be connected to 91 and terminal 32 must be connected to 92. Electrical wirering can be seen in the drawing below.

4.5 Current output

A true HART signal consists of a Current output combined with a HART FSK signal. In order to achieve this, connections must be made according to the chapter: HART electrical connections. When a HART module is installed the Current output changes its behaviour in order to comply with HART. This will be explained in the following chapters.

Terminal Description

91 HART FSK signal + 92 HART FSK signal 31 Current output + 32 Current output -

Shield/PE Shield

4.5.1 MAG 5000 C/6000 When the HART module is inserted, it automatically turns on the Current output with its factory

settings. The HART device with address „0“ is the only device that is allowed to control the Current output loop.

Single point:

When only one device is connected to the network, the HART short address should be set to 0. The Current output is fixed to Volume flow, which is the only process value in this device. Volume flow is also mapped to the PV reading.

4. Product interfaces

HART add-on module

Multidrop:

Multidrop mode is enabled by having the HART short address >0. If the HART short address is different from 0, the Current output will be forced to 4 mA no matter what the Current output settings are. This also means that errors can not be signalled.

4.5.2 MASS 6000 When the HART module is inserted, it automatically turns on the Current output with its factory settings. The HART device with address „0“ is the only device that is allowed to control the Current output loop.

Single point:

When only one device is connected to the network, the HART short address should be set to 0. The Current output is linked to the selected process value. From factory this is Massflow, which also is mapped to the PV reading. Other selections can be made, this will however not influence the PV, which is fixed to Massflow. In single Pant mode the Current output will have the behaviour as described in the table below.

Parameter Selection Comment

Current output: Massflow The Current output is active. This selection is

recommended. Volumeflow If one of these are selected, the Current output will Density be linked to this Procees variable. PV will remain Temperature Massflow! Fraction A Fraction B Pct. Fraction A OF F The Current output is deactivated. The Current

output is forced to 3 mA to indicate a Warning.

Current output mode: 0-20 mA Not possible.

0 mA can cause HART masters to stop

communicating or report errors. This is because

values below 4mA are used for alarms and validation

of the current loop. 4-20 mA Factory setting. 4-20 mA + Alarm Fatal errors = 1,3 mA

Pending errors = 2 mA

Warning errors = 3 mA

Multidrop:

Parameter Selection Comment

Current output: ON The Current output is active. ON is selected

automatically during power up. OF F The Current output is deactivated. The Current

output is forced to 3 mA to indicate a Warning.

Current output mode: 0-20 mA Not possible.

0 mA can cause HART masters to stop communi-

cating or report errors. This is because values

below 4 mA are used for alarms and validation of

the current loop. 4-20 mA Factory setting. 4-20 mA + Alarm Fatal errors = 1,3 mA

Pending errors = 2 mA

Warning errors = 3 mA

In single Pant mode the Current output will have the behaviour as described in the table below.

4. Product interfaces

HART add-on module

When the HART module is inserted in the device, and the transmitter is powered up, a new menu entry is available. The new menu hold all HART relevant information.

4.6 Local display

To change (or view) the HART settings from the keypad display.

1. Press [Top key] for two seconds. (NOTE: For “View” mode only, skip steps 2 & 3).

2. Type in password (1000) by pressing [Change key] two times, and then press

[Lock key] and wait for two seconds

3. The display now says “Basic settings”

4. Press [Forward key] until you reach the “HART module” menu item

5. Press [Lock key]

6. You can now cycle through all the HART settings by pressing [Forward key]

7. Press [Top key] for two seconds and you return to 1.

4. Product interfaces

HART add-on module

4. Product interfaces / 5. Device Variables / 6. Dynamic Variables

The table below describes submenus under the main menu „HART module“.4.6.1 Menu item

explanation

This Field Device does not expose any Device Variables.

4.6.2 SENSORPROM

All of the transmitter HART settings are stored in the SENSORPROM. This means that if the HART module is exchanged for another HART module, all of the relevant HART settings are kept.

The dynamic variables are fixed and can not be mapped to other than the specified PV, SV, TV and QV.

6.1 MAG 5000 C/6000

Item Value Description

HART 0-15 Device address [Factory setting: 00] short address

TAG name 8 characters Can be used to TAG the device.

TAG descriptor 16 characters Can be used to describe the TAG.

TAG date 3 bytes Can be used to date the installation.

HART x.xx Firmware version of the HART module.

SW version

6.2 MASS 6000

Meaning Units

PV Volume flow See Table: units SV Totalizer 1 See Table: units TV Totalizer 2 / Batch See Table: units QV Not implemented

Meaning Units

PV Mass flow See Table: units SV Density See Table: units TV Temperature See Table: units QV Volume flow See Table: units

5. Device Variables

6. Dynamic Variables

HART add-on module

Bit Definition

7 Device Malfunction – The device detected a serious error or failure that compromises device

operations. This flag is set whenever an error of category „Fatal Error“ is pending in the flowmeter. Detailed information can be found via HART command 48.

6 Configuration Changed – An operation was performed that changed the device’s configuration.

Any HART command, which writes information to the flowmeter, will set this flag. The flag can be reset using command 38. The flag is handled separately for each HART master (primary/ secondary). Note: In the flowmeter, the flag is NOT stored during power cycles.

5 Cold Start – A power failure or Device Reset has occurred. This flag is only set in the first

response transmitted to a Hart Master after power failure. The flag is handled separately for each HART master (primary/secondary).

4 More Status Available – More status information is available via Command 48, Read Additional

Status Information. This flag is set, whenever a transmitter specific error or warning is active in the flowmeter.

3 Loop Current Fixed – The Loop Current is being held at a fixed value and is not responding to

process variations. This flag is always set, if the transmitter is in Multidrop mode – i.e. the Hart address is not zero. This flag is also set in SingleDrop mode, if the flowmeters current output is forced in Service Mode or via Hart Command #40.

2 Loop Current Saturated – The Loop Current has reached its upper (or lower) endpoint limit

and cannot increase (or decrease) any further. This flag is set whenever the flowmeters overflow warning (error no. 30) is pending.

1 Non-Primary Variable Out of Limits – A Device Variable not mapped to the PV is beyond its

operating limits. This flag is always zero in the flowmeter (ie not used).

0 Primary Variable Out of Limits – The PV is beyound its operating limits. This flag is set

whenever the flowmeters overflow warning (error no. 30) is pending.

This chapter defines all status provided by the flowmeter including: the Device status byte; the Extended Device Status byte; and status information returned in Command 48.

7. Status Information

7.1 Device status

7.2 Extended device status

The extended device status bits are not supported by the flowmeter. Value is always zero.

7.3 Additional device status (Command

48)

Command 48 returns 25 bytes of data. Bits not listed in the table below are set to zero. For detailed USM II error number descriptions please look in the MAG/MASS manual, Literature 1 and 2.

Byte Bit Meaning Class

0 0 Set if any Warnings are active – See bytes18-21 below

1 Set if any Permanent errors are active – See bytes 14-17 below mode 2 Set if any Fatal errors are active – See bytes 1-5 below

1 0-7 USM Fatal Error 60, 61, 62, 63, 70, 71, 80, 81

(bit 0 corresponds to error 60, bit 7 to error 81) error

2 0-7 USM Fatal Error 82, 83, 84, 96, 97, 64, 65, 66

(bit 0 corresponds to error 82, bit 7 to error 66) error

3 0-7 USM Fatal Error 67, 68, 69, 72, 73, 74, 75, 76

(bit 0 corresponds to error 67, bit 7 to error 76) error 4 0-2 USM Fatal Error 77, 78, 79 (bit 0 corresponds to error 77, bit 2 to error 79) error 5 0-7 Reserved (=0) 6 0-7 Extended Device Status Not supported (=0) mode 7 0-7 Device Operating Mode Not supported (=0

)

mode 8-10 0-7 Analog Channel Saturated Not supported (=0) mode 11-13 0-7 Analog Channel Fixed Not supported (=0) mode 14 0-7 USM Permanent Error 40, 41, 42, 43, 44, 45, 46, 47

(bit 0 corresponds to error 40, bit 7 to error 47) error

15 0-7 USM Permanent Error 48, 49, 94, 95, 50, 51, 52, 53

(bit 0 corresponds to error 48, bit 7 to error 53) error

16 0-5 USM Permanent Error 54, 55, 56, 57, 58, 59

(bit 0 corresponds to error 54, bit 5 to error 59) error 17 0-7 Reserved (=0) 18 0-7 USM Warning 20, 21, 22, 23, 24, 30, 31, 90

(bit 0 corresponds to error 20, bit 7 to error 90) warning 19 0-7 USM Warning 91, 92, 93, 25, 26, 27, 28,2 9

(bit 0 corresponds to error 91, bit 7 to error 29) warning 20 0-7 USM Warning 32, 33, 34, 35, 36, 37, 38, 39

(bit 0 corresponds to error 32, bit 7 to error 39) warning 21-24 0-7 Reserved (=0)

7. Status Information

HART add-on module

8. Universal Commands

Command Number Data in Command Data in Response and Funktion 0 Read unique identifier None Byte 0 "254" (expansion)

Byte 1 Manufacturer ID Byte 2 Mfr. device. Type Byte 3 Number of preamble Byte 4 Universal Command

revision

Byte 5 transmitter specific

command revision Byte 6 software revision Byte 7 hardware revision Byte 8 device function flag Byte -11 Device ID number

1 Read primary variable None Byte 0 PV unit code

Byte 1-4 Primary variable

2 Read Current & None Byte 0-3 current (mA) % of range Byte 4-7 % of range 3 Read Current & None Byte 0-3 Current four variables Byte 4 PV unit code

Byte 5-7 PV Byte 9 SV unit code Byte 10-13 SV Byte 14 TV unit code etc. Byte 15-18 TV Byte 19 QV unit code etc. Byte 20-23 QV

6 Write polling address Byte 0 =Short address As in command 11 Read unique id Byte 0-5 As Command 0

associated with tag TAG (8 characters)

12 Read message None Byte 0-23 Message 13 Read Tag, Descriptor & None Byte 0-5 Tag

Date Byte 6-17 descriptor

Byte 18-20 date

14 Read PV sensor number None Byte 0-2 sensor serial number

Byte 3 unit code for sensor limits

and min. span Byte 4-7 upper sensor limit Byte 8-11 lower sensor limit Byte 12-15 minimum span

15 Read PV output None Byte 0 alarm select code information Byte 1 transfer code

Byte 2 Upper and lower range

values unit code Byte 3-6 Upper range value Byte 7-10 Lower range value Byte 11-14 Damping value (sec) Byte 15 Write protect code = 1 Byte 16 Private-label distributor

code

16 Read final assembly None Byte 0-2 Final assembly number number 17 Write Message Byte 0-23 As in command

Message 18 Write tag, descriptor Byte 0-5 As in command and date TAG

Byte 6-17

Descriptor

Byte 18-20

Date 19 Write final assembly Byte 0-2 As in command number Final assembly number

This device supports the following Universal Commands.

HART add-on module

9. Common-Practice Commands

This device supports the following Common-Practice Commands.

Command Number and Data in Command Data in reply Function

33 Read transmitter variables Not implemented 34 Write damping value Byte 0-3 Byte 0-1 As in command

Damping value in sec.

35 Write range values Byte 0 range unit code As in command

Byte 1-4 upper range Byte 5-8 lower range

36 Set upper range Not implemented 37 Set lower range Not implemented 38 Reset config. Flag None None 39 EEPROM control Byte 0 0= burn EEPROM As in command

1= restore from EEPROM 40 Enter/exit fixed Byte 0-3 Current (mA) Byte 0-3 Actual current (mA) current mode Current = 0 ⇒ Exit fixed On exit (Data in command = 0),

Current mode the response is always 4 mA 41 Perform transmitter Not implemented self-test 42 Perform master reset None None (Set to default) (Busy for approx. 30 seconds

after reply)

43 Set PV zero None None

HART will respond, command not implemented“ in the cases that PV zero is not supported by the application.

44 Write PV units Byte 0 PV units code As in command 45 Trim DAC Zero Not implemented 46 Trim DAC gain Not implemented 47 Write transfer function Not implemented 48 Read additional None See chapter 7, describing

transmitter status status information 49 Write PV sensor Not implemented serial number

50-56 Not implemented 57-58 Read/Write unit tag Not implemented 59 Write number of Byte 0 Number of response As in command

preambles preamble bytes

60-107 Not implemented 108 Write burst mode Byte 0 Burst mode command As in command

command number number

1, 2 or 3 supported

109 Burst mode control Byte 0 0 = exit, 1 = enter As in command

110 Read all dynamic None Not implemented

variables

HART add-on module 10. Device-Specific Commands

This device supports the following Device-Specific Commands. Except from command 170 and 171, these commands are reserved for software tools like PDM, AMS and HC275/375.

10. Device-Specific Commands

Command Number and Data in Command Data in reply Function

128 Read Integer8 Byte 0 CANAPP.ID Byte 0 Integer 8 value