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Issue/Rev. 0.1 (9/13) ║  MNFL003 • Page 25

Assuming that no error in communication interferes, the data field of a response from a 

slave to a master contains the requested data. If an error does occur, the field contains 

an exception code that the application controlling the master can use to determine the 

next action to be taken.

 

4.41 

Beginning Register

This register identifies the beginning register from which the master is requesting infor-

mation. This two byte field lists the most significant digit first and the least significant 

digit last. 

 

4.42 

Number of Requested Registers

This field identifies the number of consecutive registers from which the master is re-

questing information. This two byte field lists the most significant digit first and the least 

significant digit last. The response is limited to 250 bytes of information.

 

4.43 

Error Check (CRC16)

This field allows the microFlow.net Liquid and the supervisory system to check for errors in 

the transmission of commands and responses. Electrical noise or other interference may 

cause changes in transmitted data. The capacity to check for errors prevents the receiving 

device from responding to a message that has changed. 
Error checking in RTU mode is built on the Cyclical Redundancy Check (CRC) method. The 

entire message is subject to scrutiny by the CRC field, and the CRC is applied regardless 

of any other parity check method that might be in effect. 
The CRC consists of a two byte field containing a 16-bit binary value. The transmitting device 

calculates the CRC value and adds the CRC to the message. The receiving device then 

recalculates the CRC when the message is received, and compares the first value with the 

second. An error results when the two message values are unequal.
The CRC is initiated by pre-loading a 16-bit register to all 1’s. Successive 8-bit bytes 

of the message are then applied to the current contents of the register. The CRC is 

generated only by the eight bits of data in each character. Start and stop bits, and the 

parity bit if one is used, are not taken into account.
When the CRC is generated, each 8-bit character is exclusive ORed with the register 

contents. The result is then shifted toward the least significant bit (LSB), and a zero 

added to the most significant bit (MSB) position. The LSB is extracted and examined. 

Assuming the LSB was a 1, the register is then exclusive ORed with a preset, fixed 

value. If the LSB was a 0, there will be no exclusive OR.
The process consists of eight shifts. After the eighth and final shift, the next 8-bit byte 

is exclusive ORed with the register’s current value. The process is then repeated for an 

additional eight shifts. The final content of the register, after all the bytes of the message 

have been applied, is the CRC value.

 

4.5 

Placing the CRC into the Message

When the 16-bit CRC (2 8-bit bytes) is transmitted in the message, the low-order byte 

will be transmitted first, followed by the high-order byte. For example, if the CRC value 

is 1241 hex (0001 0010 0100 0001):

Addr

Func

Data 

Count

Data

Data

Data

Data

CRC

Lo

CRC

Hi

     

             

 

 

 

 

   41 

 12

microFlow.net Liquid Modbus Communications Manual 

 

 

Appendix

Summary of Contents for Smith Meter microFlow.net Liquid

Page 1: ...Bulletin MNFL003 Issue Rev 0 1 9 13 Electronic Preset Delivery System Smith Meter microFlow net Liquid Modbus and Modbus TCP Communications ...

Page 2: ...for customer information The information herein shall not be duplicated used or disclosed without prior permission of FMC Technologies Measurement Solutions Inc FMC Technologies Measurement Solutions Inc will not be held responsible for loss of liquid or for damage of any kind or from any cause to the person or property of others or for loss or profit or loss of use or any other special incidental...

Page 3: ...xplicit Logout Command 9 2 25 Set Time Date 10 2 26 Alarm Clearing 10 2 27 Other Host Clearable Flags Program Change Power Fail Transaction Batch Done etc 10 2 28 Set Max Transaction Amount 10 2 29 Allocate Recipes 10 2 30 Batch Preset Authorization Options 11 2 31 Read Transaction Log 11 2 32 Read Event Log 12 2 33 Read Audit Log 12 3 Modbus Register Reference 13 4 Appendix 22 4 1 Modbus Communic...

Page 4: ...0 04 Read Input Registers 31 5 1 05 Force Single Relay 31 5 2 06 Preset Single Register 32 5 3 15 0F Hex Force Multiple Relays 33 5 4 16 10 Hex Preset Multiple Registers 34 5 5 Exception Responses 35 5 6 How to access 64 bit information using Modbus when Modbus will only read 32 bit information 36 6 Related Publications 37 microFlow net Liquid Modbus Communications Manual Table of Contents ...

Page 5: ... which wish to obtain high peak transfer rates are instead encouraged to establish multiple TCP connections to the same target however some existing client devices are known to attempt to pipeline requests Design techniques which allow a server to accommodate this behavior are described in Appendix A The Modbus slave address field is replaced by a single byte Unit Identifier which may be used to c...

Page 6: ...pting control plus transaction control requiring authorization from host Allows use of AU or AP Authorize Authorize to Preset or SB Set Batch to enter the preset remotely Xon Xoff For printer ports only Xon Xoff flow control PTB FX For printer ports only Security level designed to support PTB compliant printers PTB LQ For printer ports only Security level designed to support PTB compliant printers...

Page 7: ...the Main Menu select Program Mode Menu and press Enter Enter the Access Code when prompted and press Enter From the Program Mode menu select Comm Directory and Press Enter Select Host Interface and press Enter From the Host interface Menu set the following items Host Interface IP Address 192 168 0 1 Net mask 255 255 255 0 Gateway 192 168 0 10 Ethernet Control Poll and Program Comm Link Level 3 Ret...

Page 8: ...s 2 2 Implementing Host Control Automation Interface via Modbus 2 21 Special Modbus Registers for Host Control Certain registers are trigger registers that invoke a host automation command such as a prompting function or a remote authorization function These registers are listed here Note that some of these trigger registers require other registers have valid argument values prior to invoking the ...

Page 9: ...Security Access Not Available 96 Internal Error 2 23 Program Mode Interface Entering Program Mode via Modbus Entry to Program mode via Modbus is done by simply writing a value to a configuration register in the map assuming all security requirements are met Each write to the con figuration restarts the auto logout timer If three seconds transpire with no additional updates writes it is assumed by ...

Page 10: ...on Write of 0 2 Program Mode Value Changed 3 Power fail Occurred 259 Batch Done 260 Transaction Done 2 28 Set Max Transaction Amount Write the maximum total amount allowed for the transaction when host authorization of type AU AP will be issued i e the operator driver will determine batch sizes 9F00 9F01 40704 40705 TA Set Transaction Maximum Amount unsigned long integer Range is 0 99 999 Note The...

Page 11: ...dbus locations for both current and his torical transactions Hence historical transaction data should only be requested during idle periods Also to read current data the Transaction Select register MUST BE SET TO 0 After reading historic transaction log data be sure to set the host transaction select register back to 0 to be able to read current run data To retrieve transaction data Write host tra...

Page 12: ... Reading from the Audit Log uses the same procedure as reading from the Event Log Replace the register numbers for the most recent entry and the request with theAudit Log equivalents the entry itself is read from the same location for both the Event and Audit logs The most recent Audit Log entry s sequence number can be read via Function 4 registers 1794 1795 unsigned long integer To read an entry...

Page 13: ...ilure 2581 0A15 PR Pressure Transducer Fail 2582 0A16 HF High Flow Alarm 2583 0A17 HT High Temperature Alarm 2584 0A18 HD High Density Alarm 2585 0A19 HP High Pressure Alarm 2586 0A1A LF Low Flow ALarm 2587 0A1B LT Low Temperature Alarm 2588 0A1C LD Low Density Alarm 2589 0A1D LP Low Pressure Alarm 2590 0A1E MF Mass Meter Comm Fail 2591 0A1F MO Mass Meter Overdrive 2592 0A20 MT Mass Meter Tube Fai...

Page 14: ...er Pulse Width 7708 1E1C 145 Sampler Disable Program Configuration etc HOLDING REGISTERS Function 3 6 16 table Dec Hex Parameter and Description Directory DIGITAL_DIR Data Type UNSIGNED_CHAR Start Address 3584 3584 0E00 201 Input 1 DC Function Select 3585 0E01 202 Input 2 DC Function Select 3586 0E02 203 Input 3 DC Function Select 3587 0E03 301 Output 1 DC Function Select 3588 0E04 302 Output 2 DC...

Page 15: ...ensity Alarm 13834 360A 639 Low Density Alarm 13835 360B 640 Density Transducer Alarm 13836 360C 641 High Pressure Alarm 13837 360D 642 Low Pressure Alarm 13838 360E 643 Pres Transducer Alarm 13839 360F 651 Pulse Security Alarm 13840 3610 652 Mass Mtr Comm Alarm 13841 3611 653 Mass Mtr Overdrive Alarm 13842 3612 654 Mass Mtr Tube Alarm 13843 3613 665 Additive Feedback Error 13844 3614 666 Additive...

Page 16: ...ow Start Rate 21250 5302 203 Low Flow Start Amount 21252 5304 204 Low Flow Start of Batch 21254 5306 223 Overrun Alarm Limit Directory LOAD_ARM_DIR Data Type UNSIGNED_CHAR Start Address 22016 22016 5600 151 Permissive 1 Sense 22017 5601 153 Permissive 2 Sense 22018 5602 231 Zero Flow Timer 22019 5603 232 Valve Fault Timeout 22020 5604 731 Report Select 22021 5605 732 Report Total Resolution 22022 ...

Page 17: ...ssure 1 25410 6342 523 Vapor Press Temp 1 25412 6344 524 Vapor Pressure 2 25414 6346 525 Vapor Press Temp 2 25416 6348 526 Vapor Pressure 3 25418 634A 527 Vapor Press Temp 3 25420 634C 321 Maintenance BS W 25422 634E 322 BS W Hi Alarm Limit Directory PRODUCT_DIR Data Type UNSIGNED_CHAR Start Address 26112 26112 6600 351 Meter Factor Variation Select 26113 6601 412 API Table 26114 6602 511 Min BP F...

Page 18: ...Mode Logout 40578 9E82 AU AP SB SF Host Authorize 40587 9E8B Archived Transaction Retrieval Number Back 0 current 40588 9E8C Recipe Index to Read Write 1 4 Start of Function 4 STATUS REGISTERS Function 4 table Dec Hex Description Directory SYS_RUN_DATA Data Type TEXT Start Address 0 0 0000 Card Data Pt 1 16 0010 Card Data Pt 2 32 0020 Time of Last Power Fail 48 0030 Requested Audit Event Log Entry...

Page 19: ...Load Average BS W 2840 0B18 Original Ref Den 2842 0B1A Original BS W Directory TRAN_RUN_DATA Data Type DOUBLE Start Address 3072 3072 0C00 Indicated Volume IV 3076 0C04 Gross Volume GV 3080 0C08 Gross Std Temp Volume GST 3084 0C0C Gross Std Temp Press GSV 3088 0C10 Mass 3092 0C14 Additive 1 Volume 3096 0C18 Additive 2 Volume 3100 0C1C Additive 3 Volume 3104 0C20 Additive 4 Volume 3108 0C24 Dry Std...

Page 20: ...itive 1 Volume 5148 141C Additive 2 Volume 5152 1420 Additive 3 Volume 5156 1424 Additive 4 Volume 5160 1428 Dry Std Temp Press GSV Directory BATCH_RUN_DATA Data Type UNSIGNED_CHAR Start Address 5632 5632 1600 Recipe Number 5633 1601 Batch Directory BATCH_RUN_DATA Data Type UNSIGNED_LONG Start Address 5888 5888 1700 Additive Mask Directory PRD_RUN_DATA Data Type FLOATING POINT Start Address 6912 6...

Page 21: ...3 Current of Injections Batch 11907 2E83 Inj 4 Current of Injections Batch 11908 2E84 Inj 1 Current Feedback Errors 11909 2E85 Inj 2 Current Feedback Errors 11910 2E86 Inj 3 Current Feedback Errors Directory ANA_RUN_DATA Data Type FLOATING POINT Start Address 15104 15104 3B00 Analog Analog Counts 15106 3B02 Analog Raw Value mA or volts 15108 3B04 Analog Engineering Value 15136 3B20 Analog I O 2 An...

Page 22: ...onse and the data bytes contain a code that describes the error The error check field allows the master to confirm that the message contents are valid 4 11 RTU Framing Every Modbus message begins with a silent interval of at least 3 5 character times Multiply the character times by the current network baud rate to determine the length of the silent interval see T1 T2 T3 T4 in the figure below Next...

Page 23: ...d Relay Status Reads the binary data from the read write set of variables 02 Read Input Status Reads the binary data from the inputs read only set of variables 03 Read Integer Registers Read Write Register Set Retrieves the current data from the request ed registers 04 Read Integer Registers Read Only Register Set Retrieves the current data from the request ed registers 05 Force Single Relay Chang...

Page 24: ... an invalid data addressfor the microFlow net Liquid A listing of the exception codes appears below Code Name Meaning 01 Illegal Function The function code received in the query is not an allowable action for the slave If a Poll Program Complete command was issued this code indi cates that no program function preceded it 02 Illegal Data Address The data address received in the query is not an allo...

Page 25: ...ining a 16 bit binary value The transmitting device calculates the CRC value and adds the CRC to the message The receiving device then recalculates the CRC when the message is received and compares the first value with the second An error results when the two message values are unequal The CRC is initiated by pre loading a 16 bit register to all 1 s Successive 8 bit bytes of the message are then a...

Page 26: ...ntents including the byte count field The microFlow net Liquid response example illustrates a typical byte count field in a normal response Master Query Field Name Example Hex RTU 8 Bit Field Header None microFlow net Liquid Address 06 0000 0110 Function 03 0000 0011 Starting Address Hi 00 0000 0000 Starting Address Lo 6B 0110 1011 No of Registers Hi 00 0000 0000 No of Registers Lo 03 0000 0011 Er...

Page 27: ...e byte count 4 61 Byte Count The byte count is sent to the master supervisory system indicating how much data is being sent from the microFlow net Liquid In the example shown the command requested data from these registers and each register contains two bytes of data 4 62 Data Register Each of the data registers of unsigned characters contains two bytes of data The response message returns the dat...

Page 28: ...pecifies the relay addressed in the query All other relays follow from low order to high order in subsequent bytes The returned relay quantity must be a multiple of eight otherwise it will be padded with zeros toward the high order end of the byte The assembled bytes of data are specified in the byte count field An example of a response to the preceding query appears below Response Field Name Exam...

Page 29: ... 16 are addressed as 0 through 15 An example of a request to read the status of inputs 1024 to 1033 from microFlow net Liquid 17 is shown below Query Field Name Example Hex microFlow net Liquid Address 0x11 Function 0x02 Starting Address Hi 0x00 Starting Address Lo 0xC4 No of Points Hi 0x00 No of Points Lo 0xOA Error Check CRC calculated Response The input status is packed in the response message ...

Page 30: ... write registers Query The query message specifies the starting register and quantity of registers to be read Registers are addressed starting at zero An example of a request to read registers 107 through 109 from microFlow net Liquid 17 is shown below Query Field Name Example Hex microFlow net Liquid Address 0x11 Function 0x03 Starting Address Hi 0x00 Starting Address Lo 0x6B No of Points Hi 0x00...

Page 31: ...RC Response Each register data in the response message contains two bytes The binary contents are right justified within each byte Within each register the first byte contains the high order bits and the Second byte contains the low order bits An example of a response to the preceding query appears below Response Field Name Example Hex microFlow net Liquid Address 11 Function 04 Byte Count 02 Data...

Page 32: ...et Liquid Address 11 Function 05 Relay Address Hi 00 Relay Address Lo 96 Force Data Hi FF Force Data Lo 00 Error Check CRC 5 2 06 Preset Single Register Description Presets a value into a single holding register Query The query message specifies the register reference to be preset Registers are ad dressed starting at zero The requested preset value is specified in the query data field An example o...

Page 33: ...ting at zero thus relay 1 is addressed as 0 The contents of the query data field specify whether a state is ON or OFF A logical 1 in a bit position of the field requests the corresponding relay to be ON A logical 0 requests that the relay be OFF An example of a request to force a series of ten relays starting at address 15 or OF hex in microFlow net Liquid 17 appears below The query data content c...

Page 34: ...nse to the preceding query appears below Response Field Name Example Hex microFlow net Liquid Address 11 Function 0F Relay Address Hi 00 Relay Address Lo 01 Quantity of Relays Hi 00 Quantity of Relays Lo 0A Error Check CRC 5 4 16 10 Hex Preset Multiple Registers Description Presets values into a sequence of holding registers Query The query message specifies the register references to be preset Re...

Page 35: ... 1 The microFlow net Liquid receives the query with no communication errors handles the query normally and returns a normal response 2 A communication error bars the microFlow net Liquid from receiving the query so no response is returned The master program eventually processes a timeout condition for the query 3 The microFlow net Liquid receives the query without error but returns no response The...

Page 36: ...ifies that only one relay is to be read 5 6 How to access 64 bit information using Modbus when Modbus will only read 32 bit information 64 bit information is referring to double precision data which is the data type of most volumes as well as a lot of other data stored in the preset 32 bit information is referring to single precision data The answer to this problem is to save each double precision...

Page 37: ...at measurement fulfillment fmcti com or online at www fmctechnologies com measurementsolutions When requesting literature from Literature Fulfillment please reference the appropriate bulletin number and title microFlow net Liquid Specification Bulletin SS06047 Installation Bulletin MNFL001 Communications Bulletin MNFL002 Modbus Communications Bulletin MNFL003 Operator Reference Bulletin MNFL004 Op...

Page 38: ...asurementsolutions and click on the Contact Us link in the left hand column Headquarters 500 North Sam Houston Parkway West Suite 100 Houston TX 77067 USA Phone 1 281 260 2190 Fax 1 281 260 2191 Ellerbek Germany 49 4101 3040 Erie PA USA 1 814 898 5000 Integrated Measurement Systems Corpus Christi TX USA 1 361 289 3400 Kongsberg Norway 47 32 286700 Operations Measurement Products and Equipment Prin...

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