Advantech ADAM-6018 8-Channel Isolated Thermocouple Input Modbus TCP Module with 8-Channel Digital Output ADAM-6018-BE Data Sheet

ADAM-6000 and ADAM-5000/TCP system accept a command/response 
form with the host computer. When systems are not transmitting they are 
in listen mode. The host issues a command to a system with a specified 
address and waits a certain amount of time for the system to respond. If 
no response arrives, a time-out aborts the sequence and returns control to 
the host. This chapter explains the structure of the commands with Mod-
bus/TCP protocol, and you can refer to the example codes provided by 
.NET class library to see how to write or read Modbus/TCP address of 
ADAM-6000 modules. The examples are in the folder listed below: 

Windows win32 operating system (such as windows 2000/XP/Vista):
Program Files\Advantech\Adam.NET Class Library\VS2003\sam-
ples\Win32\VB\ModbusTCP
Program Files\Advantech\Adam.NET Class Library\VS2003\sam-
ples\Win32\Vc#\ModbusTCP

Windows CE.NET operating system:
Program Files\Advantech\Adam.NET Class Library\VS2003\sam-
ples\WinCE\VB\ModbusTCP
Program Files\Advantech\Adam.NET Class Library\VS2003\sam-
ples\WinCE\Vc#\ModbusTCP

Note: Please refer to Appendix B.2 for the Modbus/TCP address of 
ADAM-6000 modules.

It is important to understand the encapsulation of a Modbus request or 
response carried on the Modbus/TCP network. A complete command is 
consisted of command head and command body. The command head is 
prefixed by six bytes and responded to pack Modbus format; the com-
mand body defines target device and requested action. Following exam-
ple will help you to realize this structure quickly.