Thermo Electron Ramsey Micro-Tech 3000 Series, Serial Communications Manual

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Serial Communications 3101/3201
REC XXXXX 3-18
3.4 Communication Protocols
The communication protocol allows a remote intelligent device to read and eventually write the
contents of the registers as listed in this section.
During the communication activity, the Micro-Tech 3000 always acts as Slave, meaning that it
will respond to a request from a Master device on the line, but never attempts to send
messages out.
The instrument responds only if the message is completely received. The instrument reads
the message and looks for the address, which is contained in an address byte in the query
package. The message is then processed only if the address contained in the message
matches the address specified in the set-up data of the instrument. When the system
receives a message, the integrity of it is checked, and an answer message is prepared if yes.
The Master must respect a 100 ms interval time between two messages. If a message is sent
before 100 ms have passed since the previous one, it is lost. (The data is received by an
interrupt routine, while it is processed in a task which is executed each 100 ms.)
If the Master sends variables to be written in memory, the system checks the correctness of
the message, and immediately sends an answer message if it is correct. This does not
necessarily mean that the data is written in memory. The system first checks the address,
which must correspond to a valid address of a variable, then the minimum and maximum limits
are checked, and then the password. If data can be accepted, the success flag is set to 0 (no
error), if not, it is set to 1. The Master needs to check the success flag (contained into a read
only register), to know if the last variables sent have been stored or not.
The procedure is as follows:
- Send the data to the Micro-Tech 3000
- Wait 100 ms
- Read the success flag, should be 0.
Some data is read only, some is read write, some is write only.
NOTE: The maximum number of words the system can transfer is 41 per time.
Requests of registers in excess of 41 are treated as errors and do not generate an
answer.
NOTE: This section only applies to multidrop operation. If you are using the COMM
option for connecting a Printer, skip this section and refer to Section 3.3.4.