Manual Weighing Controller A 810
A.S.T. Angewandte SYSTEM-TECHNIK GmbH Dresden
Page
77
4.4.2. Foreign Remote Display Units
Any A810 terminal can in principle be adapted by the manufacturer to any remote display unit and its
protocol. This will be done on customer's demand. Altogether up to 8 different data exchange protocols
can be declared and selected by the commissioning program. The remote display can read out either
gross, net or tare weight or the value currently on display.
4.5. PC / SPC
Linking an A810 terminal to the serial interface of a computer or a stored-program control unit allows
weighing data to be used in data processing or process control. In this case the computer or the control
unit is commonly the active party that triggers certain reactions of the terminal by means of a set of
declared commands. The default setting of an A810 terminal is such that it will transmit data only in case
of error when no request is received.
4.5.1. Acknowledgement Protocol
By issuing an acknowledgement protocol the terminal reports back to the computer whether it has
understood a transmitted command. The default setting when a terminal is supplied is such that each
command is acknowledged after 25 ms at the latest by character Acknowledge (ACK, code 06h) when it
is valid or character Negative Acknowledge (NAK, code 15h) when the command cannot be executed.
Please note that the transmission of character ACK does not prove the meaning of the transmitted data to
be correct. The acknowledgement protocol can be changed during in the commissioning program. The
same applies to the run time (command ‘PROTOK’).
4.5.2. Structure of a Data Frame
Data frames have identical structures in either direction. Each of them contains the following components:
block header data record end of block
The default setting when a terminal is supplied is character STX (code 02h) for the block header and
character ETX (code 03h) for the end-of-block code. This declaration can be changed in the
commissioning program and during traffic (command 'LINES'). The data record contains the information
to be transferred. It consists of a command transmitted to A810 and a data record returned in response.
The characters belonging to a data block shall be transmitted to the terminal within one second, otherwise
the terminal will regard the transmission as finished, reply by transmitting NAK and ignore the block.
4.5.3. Remote Control Commands
Each of the remote control command starts with a command number (see Table 3). Depending on the
type of command, more parameters may follow. For those commands that request a terminal to transmit
a data record, the structure of the returned data record will be explained when describing the command.
A A810 is able to receive several commands directly following one another and to execute them
subsequently. The order of the responses need not necessarily coincide with the order of the commands
since the response may depend on certain conditions such as dwell.
In the following passage all numbers used in a command are represented as hexadecimal numbers or
ASCII characters. The examples contain only the data records. The block headers and end-of-block
codes have to be added in accordance with the block structure used.
Summary of Contents for a810
Page 2: ......
