Cangnan Instrument Flow Meter MODBUS Communication Protocol

Protocol Overview

1.1 MODBUSminite(BCD),sec(BCD), bkflag(byte),0, CRCGB/Z L, Represented by F (Float): FloatData=± 0. MH-MM-ML * 2PStandard .                             

1.2This agreement applies to our factoryLWQZGas intelligent turbine flowmeter,  LLQZIntelligent Roots flowmeter,  LUXZIntelligent spiral vortex flow

Calculation,  EVCVolume correction devices and other products.

1.3Main characteristics

Device attributes: The flow meter isMODBUSSlave stations on the communication bus

Communication mode: RTU

Communication media: RS485

mailing address: 1-247

Baud rate:  1200 , 2400 , 4800 , 9600 , 19200 bps

Data bits:  8Position

Checksum:  No verification(2A stop position), Occasional verification(1A stop position), Odd verification(1A stop position)

1.4 specific characteristics

This agreement is developed for flow meters, Support multi byte binary numbers, ASCIIcharacter string, BCDData communication of code and other types of variables;  Communication selectionMODBUSof Function code03H , 07HAnd add user-defined options, Function code66HSupported by.

Function codeMODBUSFunction code

The data frame format is as follows:, Function code:

2.1 Read the starting address at03: Rise upstart_addrIndividual character dataNSee table. Sent by the main station1.

Response from the station: addr, 03, start_addr_hi ,start_addr_low, N_hi,N_low, CRC

Abnormal response:  addr, 03, num, data(0),… .,data(num- 1), CRC

Table: addr, 83H, error_code, CRC

Register address1

Variable name	Number of registers	TypeN	Company	Accumulated operating conditions
0000H	Accumulated quantity of standard conditions	4	BIN	3
0004H	Operating flow rate	4	BIN	Nm3
0008H	Standard flow rate	2	BIN	m3/h
000AH	Temperature	2	BIN	Nm3/h
000CH	Pressure	2	BIN	℃
000EH	Among them	2	BIN	kPa

starting address:

  starting address: Fromstart_addr_hi , start_addr_low

2Composed of bytes, The high byte of the starting address in sequence, Low byte; The starting address must be the value in column 1 of Table 1, Otherwise, the flow meter will reply with an incorrect address(error_code =2); FromN_hi , N_low 2Composed of bytes, Read N words(1Data consisting of 2 bytes per character;

     num : Indicate the number of data points, data(i) , i=0,…,num, num＝2N.

     error_codePlease refer to the table for the code4.

Example1  (Factory default:  CodFor01 , CdrFor23 , bpsFor9600)

   Sent by the main station:   17      03        00 04         00 04          073E  

Address Function code  Number of starting address registers CRCVerification code

  Response from the station: 17       03       08       00000039412524E1    9D25

Number of bytes in the address function code   Accumulated quantity of standard conditions   Verification code

  The variable data is a standard cumulative flow represented by an 8-byte binary number, High position first, The first 6 bytes are integer parts, The last two

One is the decimal part, Unpackaged data3752229. 144Nm3/h.

  Please provide instructions for unpacking the attached data:

1) Integer part hexadecimal number00 00 00 39 41 25Equivalent to decimal system3752229.

2) Decimal hexadecimal numbers(24 E1) 16 = (9441)10 / 65536= 0. 14405(Decimal decimals).

3) The result is:3752229.14, Company: Nm3/h

Example2Read register data (in this example, read the data displayed by the current integrator)

  send from the master station:   17       03         00 00         00 10          46F0   

address function code  number of starting address registers  CRCchecksum

  slave station response: 17       03         20          00 00 00 37 12 05 A0 43     00 00 00 37 12 05 A0 43

address function code  number of received bytes   operating condition cumulative quantity        standard condition cumulative quantity

00 01 CB 6B     00 01 CB 89      00 00 14 00    00 00 65 53    BA 18 

operating condition flow rate   standard condition flow rate    temperature    pressure   checksum

remark: when the data frame sent by the master station is incorrect, the slave station does not responderror_codecode, at this time, refuse the master to continue sending commands.

2.2 Function code07, Reading flow meters1Byte by byte status data. See table2.

Sent by the main station: addr, 07, CRC

Response from the station: addr, 07,status, CRC

Table2

2.3Function code66H, User defined function codes, Used to read historical data inside the flowmeter. See table3.

Table3

2.3.1Read the latest Mth real-time record(1Record entries)

Sent by the main station: addr, 66H, 00, 64H, 02H,M_hi, M_low, CRC

Response from the station: addr,66H ,22H,psum(BIN),sum(BIN),q0(BIN),t(BIN),p(BIN),year(BCD),month(BCD), day(BCD),hour(BCD),minite(BCD),sec(BCD), CRC

2.3.2Read the records from the past M months(1Record entries)

Sent by the main station: addr, 66H, 00, 65H, 02H, M_hi,M_low, CRC

Response from the station: addr,66H, 0AH, sum(BIN), year(BCD), month(BCD), CRC

2.3.3Read the latest Mth start/stop record(EVCNo start stop record, 1Record entries)

Sent by the main station: addr, 66H, 00, 66H, 02H,M_hi, M_low, CRC

Response from the station: addr,66H,10H,sum(BIN),year(BCD),month(BCD),day(BCD),hour(BCD),

minite(BCD),sec(BCD), ssflag(byte),0, CRC

2.3.4Read the record of the latest M-th sensor being cut or connected(1Record entries, Only applicable to intelligent integrators equipped with mechanical counters) Sent by the main station: addr, 66H, 00, 67H, 02H,M_hi, M_low, CRC

Response from the station: addr,66H,08H ,year(BCD),month(BCD),day(BCD),hour(BCD),

minite(BCD),sec(BCD), bkflag(byte),0, CRC

remarks:

     MAs a character, Represented by 2 bytes, M_hiFor high byte, M_lowFor low bytes, When reading the latest record, M=1,

WhenM=0When it is greater than the number of records stored inside the flowmeter, The flow meter returns a sequence with a value of 0.

     psum(BIN),sum(BIN): Accumulated quantity represented by 8-bit binary numbers, High position first, The first 6 bytes are integers, The last two

Byte is a decimal, Company: m3.

     q0(BIN): Instantaneous flow rate under standard conditions represented by 4-byte 8-bit binary numbers, High position first, The first three bytes are integers, The last byte

For decimals; Company: Nm3/h.

     t(BIN): Temperature represented by 4-byte 8-bit binary number, High position first, The first three bytes are integers, The last byte is a decimal; Single

Position: ℃.

     p(BIN): Pressure represented by 4-byte 8-bit binary numbers, High position first, The first three bytes are integers, The last byte is a decimal; Single

Position: KPa.

year,month,day,hour,minite,sec

For single byteBCDCode, Representing the year (starting from year2000not displayed, 20month), day, hour, minute, second, marked as start/stop.

ssflagwhen, hourssflag＝55Hmarked as start record, when; hourssflag＝0EEHmarked as stop record, marked as normal/cut off.

bkflagwhen), Whenbkflag＝55HTime, This record indicates that the sensor connection has been restored to normal; Whenbkflag＝

0EEHTime, This record indicates that the sensor connection was cut off.

Note:1: Record the starting time: Used to specify the starting time for real-time recording, 2Bytes, Hour minute; The default second time is0;

Note:2: Current time: Year Month Day Hour Minute Second, 6Bytes, BCDCode, Among them, the year is 1 byte (starting from year2000not displayed, 20note):  instrument production information3: byte: 36code, ASCIIincluding manufacturer code; word10product model, byte12product serial number 8 bytes, software version 3 bytes,

production date 3 bytes (year, month, day, note);

real-time record4: one real-time data record total

: byte34including cumulative quantity of working conditions 8 bytes, bit binary number(8unit, standard condition accumulation: m3 ), quantity 8 bytes bit binary number(8unit, instantaneous flow rate 4 bytes: m3 ), bit binary number(8unit, temperature: m3/h), byte4 bit binary system number(8unit, pressure 4 bytes: ℃), bit binary number(8unit, time 6 bytes: kPa), code( BCDyear, month, and year). Day, hour, minute, and second, note)

monthly record5: one month record in total;

bytes10cumulative amount of standard conditions 8 bytes, binary digits(8Binary digit, Company: m3 ), Time 2 bytes(BCDCode, Year

Month)

Note:6: Start stop record: A total of one start stop record15Bytes, Accumulated standard quantity of 8 bytes(8Binary digit, Company: m3 ), Six words of time Festival(BCDCode, Year Month Day Hour Minute Second), Start stop mark 1 byte(55HIndicating that traffic has grown from scratch, EEHIndicate the flow from presence to absence) , 0(Reserved bytes);

Note:7: Anti cutting record: One anti shear record consists of 8 bytes in total, Time 6 bytes(BCDCode, Year Month Day Hour Minute Second), Anti shear marking1  Bytes(55HIndicates that the sensor harness is connected, Under normal circumstances; EEHIndicates that the sensor harness has been cut off, For abnormal situations; record The time is the time when it is connected or disconnected), 0(Reserved bytes).

2.4  Several situations where the flowmeter does not respond after receiving a communication frame:

2.4.1When the communication address byte of the received data frame is different from the local address;

2.4.2The communication address byte for receiving a data frame (equal to0)when it is a broadcast address;

2.4.3when it receives a data frameCRCwhen there is a verification error;

2.5.4when the command code for receiving a data frame is incorrect.

2.5 when an exception is detected

when the slave receives a data frame sent to the local machine, CRCwhen the verification is correct, when an exception is detected,

the slave response is: addr, function_code+128,error_code,CRC

note: function_code: is the function code in the host command frame (the second byte), function_code+128the highest position of the byte

represents the exception1, table;

value4

there are three types of data in the table

code and:     BIN , BCDCode andASCIICode:

3.1 , BIN : Binary numbers, High byte first, Low byte after; There are four situations respectively:

1Byte (without decimals, unsigned);

2byte (without decimals, unsigned);

4byte (last 1 byte represents decimals, the highest bit of the first byte represents the sign bit, 1represents negative numbers, 0represents positive numbers).        8byte (last 2 bytes represent decimals, unsigned bits; the last 2 bytes represent decimals

one word after the decimal place of the real-time recorded cumulative quantity and standard cumulative quantity00, default).

3.2 , BCDdecimal place is calculated as one byte: 1code, byte represents two digits9.

3.3 , ASCIIvalue range is 0- : code, 8character, bitASCIIone byte, code.

represents one English letter or number

special instructions, compatible with the original custom flowmeter communication protocol:

4.1, adds a special instruction format, data bit is 8. no parity checkCodcommunication mode10.

4.2, set to(ADDR)flowmeter address023, factory default value is17.

4.3 , 02i.e. hexadecimal

4.3.1 , command to read measurement parameters:

55H, 55H, ADDR, 02 , 00, ChkSum

4.3.2, upper computer sends to flowmeter:

55H, 55H, ADDR, 02, 18, DevStatus, DevErr, Qm, Qo, t, p, sum, ChkSum

flowmeter responds to data frame to upper computer:

     55H , 55Hremarks, Guiding characters for data frames;

     ADDR Indicates the beginning of a data frame, 1Provide the communication address for the flowmeter, Bytes1—247.

     02 Value range, 1For communication command number, Bytes.

     18Read measurement parameters, 1For data length, Bytes18HIt indicates that there is something behind it.

     Qm(A byte of data) , Qo(Operating flow rate) , t(Standard flow rate) , p(Temperature) , sum(Pressure).

     ChkSum  Accumulated quantity, 1To verify the sum, Its value is fromAddressUp toChkSumThe lower 8 bits of the sum of all previous data;       DevStatus : For status code, 1Bytes, The meanings of each of them are shown in the table5:

Table5

     DevErr: For fault codes , 1Bytes, The meanings of each of them are shown in the table6:

Table6

  Operating flow rate, Standard flow rate, Temperature, Pressure is represented by a 4-byte (single precision) floating-point number, In sequence:P , SMH , MM , M

L, UseF  (Float)express: FloatData = ±0.MH-MM-ML*2P

  The cumulative amount is represented by a floating point number of 6 bytes, In sequence:P , SMH , MM , ML , ML1 , ML2, UseF  (Float)express:

FloatData = ±0.MH-MM-ML-ML1-ML2*2P

Among them: P :   Rank code, 1Bytes, Represented in hexadecimal complement format.

SMH : The high byte of the last digit, 1Bytes, The highest bit (7th bit) is the sign bitS , S=1 Indicates that the data is negative, S=0 Then the data is positive; The remaining 7 bits are the upper 7 bits of the floating-point number tail, Position 0 to 6.

MM  : The middle byte of the tail, 1Bytes, 7th to14Position.

ML  :  The low byte of the tail, 1Bytes, The15Arrived23Position.

ML1 :  The low byte of the tail, 1Bytes, The24Arrived31Position.

ML2 :  The low byte of the tail, 1Bytes, The32Arrived39Position.

Example3:

  The data frame sent by the upper computer to the flowmeter:

55     55     17      02    00       19   

55H  55H   ADDR   CMD  Len1   ChkSum

  The data frame that the flowmeter responds to the upper computer:

55    55     17      02    18      15         00      00 00 00 00     00 00 00 00      05 50 00 00      07 65 4C CC

55H  55H  ADDR  02   18   DevStatus   DevErr     Qm          Qo          t             p

16 72 82 4A 49 25     E1

sum       ChkSum

  Divide the tail into integer and decimal parts using the decimal value of the order code as the boundary, Perform binary to decimal conversion calculations again.   

Please provide a description of the attached data package:

55 55 17 02 18          －－－

15

00

00 00 00 00 00 00 00 00 05 50 00 00

07 65 4C CC

Status code

Fault code

Instantaneous flow rate under working conditions=0

Instantaneous flow rate under standard conditions=0

Temperature=0.10100  000000000000000000×2∧0101=20

Pressure=0.1100101  0100110011001100×2∧0111＝101.29998779

16 72 82 4A 49 25      Accumulated quantity=0.1110010100000100100101  00100100100100101×2∧10110 =3752229. 1428604125

E1                       -- checksum

4.3.3  Floating point analysis of custom flowmeter communication protocol

Below is a detailed explanation on how to parse 4-byte floating-point numbers and 6-byte floating-point numbers.

Temperature:  05 50 00 00 According to the definition of data types,  P=(05)H=(0101) 2   = 5

SMH=(50)H=(01010000) 2      MM=00  ML=00

. BecauseSMHThe highest position is0, Therefore, the tail number is positive. And the order code P is converted to a decimal number5, Therefore, after converting the tail number to binary, The first 5 digits are integer parts, The rest is the decimal part.

FloatData =   0       10100       0000000000 00000000       Convert to decimal number

Positive     Integer part          Decimal part

FloatData = 1×24   + 1×22   = 20

Stress:  07 65 4C CC Among them P=(07)H =(0111) 2  =7 SMH=(65)H=(01100101) 2 MM=(4C)H=(01001100) 2 ML=(CC)H=(11001100) 2

BecauseSMHThe highest position in the middle is0, Therefore, the tail number is positive, And the order code P is converted to a decimal number7, Therefore, after converting the tail number to binary, 7 bits are integer parts, The rest is the decimal part.

FloatData = 0    1100101    01001100 11001100    Convert to decimal number

Positive   Integer part       Decimal part

FloatData= 1×26   + 1×25   + 1×22   + 1×20   + 1×2-2   + 1×2-5   + 1×2-6

+ 1×2-9   + 1×2- 10   + 1×2- 13   + 1×2- 14   = 101.29998779

Accumulated quantity: 16 72 82 4A 49 25Among them P=(16)H=(00010110) 2  = 22 SMH=(72)H=(01110010) 2                              MM=(82)H=(10000010) 2 ML=(4A)H=(01001010) 2 ML1=(49)H=(01001001) 2  ML2=(25)H=(00100101) 2 , SMHThe highest position in the middle is0, Therefore, the last digit is positive, And the order code P is converted to a decimal number22, Therefore, when the tail number is binary, have Bit is the integer part22The rest is the decimal part , Convert to decimal number.

FloatData = 0   1110010 10000010 0100101 0 01001001 00100101   Positive

Integer part         decimal part               decimal part

FloatData =1×221   + 1×220   + 1×219   + 1×216   + 1×214   + 1×28   + 1×25   + 1×22   + 1×20+ 1×2-3   + 1×2-6   + 1×2-9   + 1×2- 12   +1×2- 15   + 1×2- 17   = 3752229.1428604125