Series PC Manual V 1.0 - Rev. 3 – 03/01/01 DS Europe
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14. SERIAL COMMUNICATIONS PROTOCOL
The series PC can also be used by means of remote connection to a computer or PLC.
You can:
• use the transducer measuring functions in “remote” mode;
• do transducer personalisation;
• configure analog outputs;
The simple communications protocol allows the transducer to be part of an RS485 multi-
drop serial transmission line where there is a computer (operating as master) and one or
more sensors which operate as slaves. During the serial transmission, the protocol
function is to guarantee integrity of transmitted data, whether they be commands,
measurements or transducer replies.
All the operations listed above are carried out by establishing communication between
computer and transducer by means of a series of commands.
These commands must be an ASCII command string with a certain format.
14.1. PROTOCOL FORMAT
The protocol considers two types of message formats to be sent to the series PC
transducer: one for general commands and the other for transducer configuration type
commands.
14.2. COMMAND MESSAGE STRUCTURE
Structure of command messages to be sent from the computer to the PCS/PCR is as
follows:
Each command must begin with an ASCII message initial character, @ (0x40).
This character “@” always takes first place in the message construction.
Afterwards we need to insert the identification (ID) of the transducer to which the
command is being addressed. The ID must always be expressed as a number between “0”
and “9”, or a letter between “A” and “Z” (capital), or simply by a question mark “?” when
you wish to send a message to a transducer for which you have no identity.
The question mark, with the RS485 multi-drop serial connections (plus PCS/PCR on the
same serial line), must be used with only one transducer connected to the line at a time.
This is to avoid that all the connected transducers reply at the same time and thence
creating a totally unmanageable situation. The “?” application is the way to establish
connection with a transducer that has no ID and then afterwards designate it with one.
After identification (still in the second position of message construction) It is needed a
character equivalent to the command you wish to send to the PCS/PCR.
The ASCII character always is in the third position in the message construction.
There is a description of the commands, further on, in section 14.3.
The command sent to the transducer must be followed by, if present, its subject matter,
which can be formed by one or a number of ASCII characters starting from the fourth
position in the message.
The end of message must always end with “<cr>” (Carriage Return, 0x0D).
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