Qiagen FLUO SENS, Руководство пользователя

Страница: 14 / 25

Page 13 of 24
FLUO SENS integrated Manual January 2013
9 Operation
is configured and operated exclusively via MODBUS-ASCII
commands. No further operation elements are necessary.
9.1 MODBUS-ASCII
The MODBUS Protocol was developed and released by the
company MODICON in the early 1980s. It is primarily employed
in the area of process automation. Because it is an open
protocol and, if nothing else, its simple structure, it is widely
used. In the meantime, the MODBUS-IDA Organization is
responsible for the maintenance and continuing development of
the protocol. Numerous documents can be obtained.
MODBUS is based on a master/slave system. The master is a
superordinate controller, for example a PC or a programmable
controller. The MODBUS Controllers in the FLUO SENS
integrated are slave devices.
There are no bus conflicts, since only a single node sends at a
time. The master requests communication. This request can be
directed to a specific node or sent out as a message to all
nodes. The nodes receive the request and send, independently
of the type of request, a reply to the master.
MODBUS communication is implemented as follows:

M
MODBUS serial communication via serial interfaces such
as RS232, RS485

M
MODBUS ASCII codes the data using ASC-II character
set in the form of legible character chains
MODBUS works according to the Master/Slave principle. A
master can communicate with one or more slaves. Only slaves
explicitly permitted by the Master can return data to the Master.
The protocol supports both binary and 16-bit values, which are
read in block-form by the Master. Neither quality recognition, nor
time stamps are supported.