Tally T5023+ Programming Manual page 187

Additional commands (Printer) Structure of the additional commands
Requested data responses
The basic characteristics of requested data responses are that for each respon-
se a requesting control command from the printer control was recognized (for
example, request = read the MSR track, response = MSR data or error identifi-
cation). These control commands are processed in series with the other print
control commands.
The timing of the response cannot therefore be exactly specified. It depends on
internal runtimes and the mechanical execution times of the printer.
Global printer status/ special printer messages
The data of the 'global printer status' (GPS) describes a status change within the
printer control, which has been caused by an exceptional circumstance. These
exceptional circumstances can be errors, operating interruptions or operating
panel entries.
With the help of 'special printer messages' (SPM) these status changes will be
specified in more detail.
After a 'break' on the printer interface, a 'printing unit parameters' response is
created in addition to the global print status which contains information on the
configuration of the printer (for example, 'maximum form width' or 'MSR function
available/ not available').
Data for the global printer status, special printer messages or specifications for
the printing unit parameters occur spontaneously and are stored in a stack in the
printer interface until they are fetched by the system.
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T5023/5023+ - Programming Guide