Serial Mode Inquire; Parallel, Ieee 1284 Mode Inquire; Figure 20 Pe To Enq Request Timing - TransAct Ithaca 90PLUS Series Programmer's Manual

Programmer's Guide
PE
DATA
STROBE
BUSY
ACK

Figure 20 PE to ENQ request timing

5.15.2

Serial Mode Inquire

All inquire commands require a response from the printer. In serial operation, inquire commands are
responded to by an acknowledged (ACK) or not acknowledged (NAK), the command ID, and, in some
cases, status. The serial ACK or NAK responses are always uniform and followed with a command ID. This
makes the design of the host application easier.
The printer will always accept serial data even if the printer is off-line. It is possible to send inquire
commands to the printer even when it is off-line. Because inquire commands are processed before they go
in the buffer, the printer will respond even when it is busy.
In serial mode, it is desirable that the response to an inquire command be received by the host before
another inquire command is issued to the printer. When the printer receives an inquiry, it must generate a
response. If inquiries are sent to the printer too fast, the printer will spend all of its time responding to them
and have no time to print.
5.15.3

Parallel, IEEE 1284 Mode Inquire

In parallel, IEEE 1284 mode, there is a way to return status information to the host. After the host makes an
inquire request, it can activate parallel, IEEE 1284 Mode 0, reverse channel and wait for a response from
the printer. The response to an inquire command is identical to serial mode.
The printer will always accept parallel, IEEE 1284 reverse channel requests but will not accept inquire
commands when it is off-line. It is possible to obtain status when off-line by placing the printer in dynamic
response mode before the printer goes off-line. The IEEE 1284 reverse channel will then respond to status
changes even if the printer is off-line. It is also possible to configure the printer, so it will not go off-line in
most cases. Power off, paper out, and faults will always generate off-line status.
11/07/05
PcOS Series 90PLUS
ID
Rev Q
Printer Control Codes
Printer Status Set/Inquire
Valid
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