M-S Cash Drawer A794 - Manual (Page 106)

A794 Owner’s Guide Chapter 6: Programming Information
December 1999 101
Status Commands
Status Command Introduction
The A794 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.
Batch Mode
For RS-232C printers, these commands enable the printer to communicate with the host
computer following the selected handshaking protocol, either DTR/DSR or
XON/XOFF. They are stored in the printer's data buffer as they are received, and are
handled by the firmware in the order in which they are received.
When a fault occurs, the printer will go busy at the RS-232C interface and not respond
to any of the Batch Mode Printer Status commands. If the fault causing the busy
condition can be cleared, such as by loading paper, or letting the thermal printhead cool
down, the printer will resume processing the data in its receive buffer.