Hach 911 User Manual page 95

Table 13 Modbus ASCII Memory Input/Output Referencing System
Reference Indicator
0xxxx
1xxxx
3xxxx
4xxxx
6xxxx
D.9 Modbus ASCII Function Codes Supported
Name
Temperature
Rainfall
pH (or ORP)
Level 1
Velocity 1
Channel 1
Channel 2
Channel 3
Channel 4 (D.O.)
Channel 5 (D.O. Temp.)
Channel 6 (Conductivity)
Channel 7 (Cond. Temp.)
Level 2
Velocity 2
Flow 1
Power
Discrete Output or Coil
Output Holding Register
Extended Memory Register
The memory data is stored in 16-bit words. Within the predefined function codes of the
Modbus ASCII protocol, the data fields are subject to interpretation by the device
manufacturer. For example, the 940 Flow Meter places temperature information in
registers 40001-40002.
Currently, the 940 Flow Meter is capable of a read-only function to retrieve channel and
total flow information. All data addresses in the Modbus ASCII message are referenced to
zero. Therefore, a reference to holding register 40001 is addressed as register 0000. The
function code field specifies the type of register accessed; therefore, the 4XXXX is implicit.
Function 03: Read Holding Registers
Reads the register (4X reference) contents of the 940 Flow Meter as defined in the tables
that follow.
Table 14 Channels' Read Holding Register Addresses
Type Size (bits)
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
Float 32
SCADA-Modbus® System Guidelines
Reference Type
Discrete Input
Input Register
Start Address
# of Registers
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Meaning
Binary
Binary
Real
Real
Real
Start Address
Hi Lo
00 00
00 02
00 04
00 06
00 08
00 0A
00 0C
00 0E
00 10
00 12
00 14
00 16
00 18
00 1A
00 20
00 26
Registers
40001-40002
40003-40004
40005-40006
40007-40008
40009-40010
40011-40012
40013-40014
40015-40016
40017-40018
40019-40020
40021-40022
40023-40024
40025-40026
40027-40028
40033-40034
40039-40040
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