Status Commands; Status Command Introduction - NCR 7158 Owner's Manual

Chapter 7: Programming Guide 7-85

Status Commands

Status Command Introduction

The 7158 has three methods of providing status to the application.
These methods are through Batch Status Commands, Real Time Status
Commands, and Auto Status Back. An application may use one or
more of these methods to understand the current status of the printer.
A brief description of each of these methods follows.
Batch Status Commands – These commands are sent to the printer and
stored in the printer's buffer. Once the printer has processed all the
previous commands these commands are processed and the proper
status is returned to the application. In the event a condition causes the
printer to go BUSY, it stops processing commands from the printer
buffer. If a Batch Status Command remained in the buffer during this
busy condition, it would not be processed. In fact, no Batch Commands
are processed while the printer is in this state.
Real-Time Commands – These commands are sent to the printer and
are NOT stored in the printer's buffer. Instead, they are acted on
immediately (regardless of the printer's BUSY status) and their
response (if any) is returned to the application. This gives the
application the ability to query the printer when it is in a busy state in
order to correct whatever fault has occurred.
Auto Status Back – This mechanism allows the application developer
to program the printer to automatically respond with a four byte status
when certain conditions in the printer change.
Please see the subsequent sections for a more detailed description of
these status commands. At the end of this Status Commands section is
a page entitled "Recognizing Data from the Printer". This describes
how to interpret what command or setting (in the case of Auto Status
Back) triggered a response from the printer.