UFM UFM-40, Installation & Operating Instructions Manual

Page: 42 / 51

Page 42 of 51
5. If there are multiple flowmeters in a data network then the basic commands cannot be used alone. The
prefix W must be added. Otherwise, multiple flowmeters will answer simultaneously, which will cause
chaos in the system.
Function prefix and function sign
Prefix P
The character P can be added before every basic command. It means that the transferred data has CRC
verification. The method of counting the verified sum is achieved by binary system addition.
For example: Command DI+(CR) (the relative binary system data is 44H, 49H, 2BH, 0DH) transferred
data is +10m3. (CR) (the relative binary system data is 2BH, 31H, 32H, 33H, 34H, 35H, 36H,
37H, 45H, 2BH, 30H, 6DH, 33H, 20H, 0DH, 0AH). And command PDI+ (CR) transferred data is
+10m3! F7 (CR), "!" means the character before it is the sum character, and the verified sum of
the two bytes after it is (2BH+31H+32H+33H+34H+35H+ 36H+37H+45H+2BH+30H+6DH+33H+20H
=(2)F7H)
Note: there can be no data before "!", and also may be a blank character.
Prefix W
Usage of prefix W: W+ numeric string address code +basic command. Value range of the numeric string is
0~65535, except 13 (0DH carriage return), 10 (0AH line feed), 42 (2AH *) and 38 (26H &). If the
instantaneous velocity of No. 12345 flowmeter is to be accessed, the command W12345DV(CR) can be
issued. Corresponding binary code is 57H, 31H, 32H, 33H, 34H, 35H, 44H, 56H and 0DH
Function sign &
Function sign & can add up to 5 basic commands (Prefix P is allowed) together to form a compound
command sent to the flowmeter together. The flowmeter will answer simultaneously. For example, if No.
4321 flowmeter is requested to simultaneously return: 1] instantaneous flow, 2] instantaneous flow
velocity, 3] positive total flow, 4] energy total, 5] AI1 analogous input current value, the following
command is issued:
W04321PDQD&PDV&PDI+&PDI-&PDIN(CR)
Simultaneously returned data are likely as follows:
+0.00m3/d! AC(CR)
+0.00m/s! 88(CR)
+10m3! F7(CR)
+0.0m3! DA(CR)
+0.0 m3! DA(CR)
9.3.2 MODBUS Communication Protocol
This MODBUS Protocol uses RTU transmission mode. The Verification Code uses CRC-16-IBM (polynomial is
X
16
+X
15
+X
2
+1, shield character is
0xA001
) which is gained by the cyclic redundancy algorithm method.
MODBUS RTU mode uses hexadecimals to transmit data.
This MODBUS Protocol uses RTU transmission mode. The Verification Code uses CRC-16-IBM (polynomial is
X
16
+X
15
+X
2
+1, shield character is
0xA001
) which is gained by the cyclic redundancy algorithm method.
MODBUS RTU mode uses hexadecimals to transmit data.
9.3.2.1 MODBUS Protocol Function Code and Format
The flow meter protocol supports the following two-function codes of the MODBUS:
Function Code Performance Data
0x03 Read register
0x06 Write single register
UFM-40 Ultrasonic transit-time flowmeter