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The serial port and protocol overview

Ultrasonic flowmeter serial and communication protocol -- MODBUS protocol.

Two MODBUS protocol format can support. Through the menu window M63, use MODBUS-RLR or MODBUS-ASCII format. By default, support MODBUS-ASCII format.

LRF-2000 series ultrasonic flow / heat meter can only support MODBUS function code 03 and 06 and the 16 three kinds of function code, are read register and write a single register and a data block write function.

For example, in RLR mode read 1 equipment flow, namely the read register 5, 6 a total of 2 registers, the command are as follows:

01030004000285 CA ( sixteen decimal digits )

Device number register number effect and function of initiation

The 85 CA is 16 hexadecimal values, in accordance with the CRC-16 ( BISYNCH, x16 + x15 + x2 polynomial is + 1 word shielding 0A001H ) cyclic redundancy algorithm is. Please refer to the MODBUS information further algorithm.

The returned data should be ( set state for simulation operation state, velocity = 1.2345678m/s ):

0103040651 3F 9E 3B 32 ( sixteen hex digits)

Device number function data bytes and data = 1.234567.

The 3F 9E 0651 four bytes is 1.2345678 IEEE754 format single precision floating point format.

For example, read net cumulative flow, REG25, REG26 two register command are as follows:

0103000400180002 44 0C ( sixteen decimal digits )

Return data should be (set net accumulator = 802609, the 4 byte 16 hexadecimal representation of 00 0C 3F 31 )

010304 3F 3100 0C A7 ED ( sixteen decimal digits )

Please note that the above example data sequence. The use of C language to explain the value, you can use the pointer directly to the desired data into the appropriate variable address can be stored sequentially, commonly used for the low byte first, such as the 1.23456m/s example above, 3F 9E 0651 data stored sequentially for 5106 9E 3F.

On the mode of ASCII read 1 equipment from register 1 the beginning of the 10 register command are as follows

: 01030000000AF2 ( CRLF )

The ": " is ASCII under the lead character, " F2 " is a double byte check and. Seek the law is in addition to the ": " all the other characters and CRLF binary ASCII code values for binary addition obtained.

In MODBUSRLR state, each up to read the 125 register. In MODBUSASCII state each time only can read out of the 61 register. If more than this number, flow meter will return an error message.

The MODBUS protocol details please refer to the relevant information.

In debugging MODBUS agreement, recommend the use of a free debugging software MODSCAN, this software can search on the Internet to. When there is a problem, if can accept to check and correct packet indicates the communication itself is not a problem.

In its default state communication setting rate is generally 9600, no parity, 8 data bits, 1 stop bit.