Printer Status Set/Inquire; Parallel, Non-Ieee 1284 Mode Inquire - TransAct Ithaca 90PLUS Series Programmer's Manual

Printer Control Codes

Printer Status Set/Inquire

5.15 Printer Status Set/Inquire
The Series 90PLUS Printer is designed to be used as part of an automated system where the host computer
makes every attempt to correct problems with the printer. In addition, the host application requires that it be able
to obtain more information from the printer than is typical of normal computer printers. A normal computer
printer does not have cash drawers and slip stations. As a result, the standard printer protocol must be extended
to deal with the additional features of a point-of-sale printer.
The Series 90PLUS Printer has defined a set of status inquiry commands that will allow a host to obtain
information about the printer and devices connected to it. The method chosen to interact with the computer is
designed to allow a reasonable approach to the host application. It will not always be possible for an existing
application to use inquire commands unless the communication drivers are available to the programmer.
All inquire commands require a response from the printer. For this reason, the parallel, non-IEEE 1284; parallel,
IEEE 1284; and serial operation of inquire commands are different. In serial and parallel, IEEE 1284 modes, all
inquire commands are responded to by acknowledged (ACK) or not acknowledged (NAK) and then the
command ID. In parallel, non-IEEE 1284 operation, the paper-error (PE) signal is driven as a response to an
inquire command.
5.15.1

Parallel, Non-IEEE 1284 Mode Inquire

There are several status inquiry commands and inquire control commands. The inquire character is treated
differently from all other characters received by the printer. Under normal operating conditions, all
information that is sent to the printer is received and placed in a holding buffer. The information stays in the
holding buffer until the printer interprets or prints it.
In parallel, non-IEEE 1284 operation there is no easy way to return complex information to the host. For
this reason, the PE signal is used for inquire responses. The FAULT signal will not be asserted by inquire
requests. If a true PE is being signaled, the FAULT line will also be driven. It is, therefore, possible to
distinguish between a paper error and an inquire response.
In parallel mode, the printer will respond to the inquire command before the parallel sequence is complete.
In other words, when the parallel port acknowledges the ID part of the inquire sequence, the PE signal will
be valid. The host must, however, remember what status was requested as the printer has no way of
signaling that information. In addition, the host must not interpret the PE signal as an error but as a response
to an inquire command.
There are two modes in which inquire responses can be signaled. These two modes result in either a
dynamic or static PE. When a dynamic PE occurs, the inquiry is sent once, and the PE signal follows the
requested status. If PE remains static, the status does not change.
Receipt paper status is always dynamic. If the PE signal is to be returned to the valid paper-error state, an
[ENQ] <4> should be issued when all other inquires are completed.
Page 80
PcOS Series 90PLUS
Rev Q
Programmer's Guide
11/07/05