© July 2017 Van Essen Instruments. All rights reserved
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5
Table 2
Diver-MOD function codes.
Function name
Function code
Function type
Read Coils
0x01 (decimal 1)
Internal Bits or Physical Coils
Write Single Coil
0x05 (decimal 5)
Internal Bits or Physical Coils
Read Input Registers
0x04 (decimal 4)
Physical Input Registers
Read Holding Registers
0x03 (decimal 3)
Internal Registers or Physical Output Registers
Write Single Register
0x06 (decimal 6)
Internal Registers or Physical Output Registers
Write Multiple Registers
0x10 (decimal 16)
Internal Registers or Physical Output Registers
2.4
Transmission Mode
The format for each byte (11 bits) for the Diver-MOD is:
Coding System: 8–bit binary
Bits per Byte: 1 start bit
8 data bits, least significant bit sent first
1 bit for parity completion
1 stop bit
2.5
Operation
The Diver-MOD acts as an interface between the Diver and a Modbus network, i.e. it converts the
Modbus commands to Diver commands and vice-versa. There is no direct communication between
the Modbus supervisory computer and the Diver. The Diver-MOD acts as a buffer between the
supervisory computer and the Diver. For example, to get a real-time value from the Diver, first a
command must be sent from the supervisory computer to the Diver-MOD. Then the Diver-MOD will
retrieve the real-time values from the Diver and store them in its internal memory. Finally, the
supervisory computer can send a command to the Diver-MOD to retrieve the real-time values.
3
Modbus Registers
All the supported Modbus registers of the Diver-MOD are listed in Appendix B. A more detailed
description of the most important registers is given below. Refer to Table 2 for the definition of the
function code.
All registers in this document are 1-based. This means the actual packets sent to the Diver-MOD
must have a data address 1 less than what the register number is in this document.
3.1
Reg. 30002, 30012: Firmware Version and Serial Number Diver-MOD
The firmware version and serial number of the Diver-MOD are stored in register 30001 and 30011