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Control Codes PcOS Series 150 Programmer's Guide
Printer Status Set/Inquire
Page 60 Rev G 12/14/99
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.
PE
DATA
STROBE
BUSY
ACK
Valid
ID Next
Figure 13 Paper-error to inquire-request timing
Serial Mode Inquire
In serial mode, inquires are not handled any differently than other commands. All inquire
commands require a response from the printer and are responded to by an acknowledged (ACK)
or not acknowledged (NAK) and then the command ID.
The serial ACK or NAK responses are always uniform and followed with a command ID. This
makes the design of the host application easier because the response can be identified and the
same format is always followed.
The printer always accepts serial data. When the printer is off-line, serial data is still accepted. It
is possible to send inquire commands to the printer even if it is off-line. Because inquire
commands are processed before they go in the buffer, the printer will respond even when it is
busy printing.
In serial mode, it is desirable that the response to an inquire be received by the host before
another inquire command is issued to the printer. When the printer receives an inquire, it must
generate a response. If inquires are sent to the printer too fast, the printer could overrun its output
buffer.
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, the host can activate parallel, IEEE 1284 Mode 0 reverse channel
and wait for a response from the printer. The response to the inquire is identical to serial mode.
The printer will always accept IEEE 1284 reverse channel requests but will not accept inquire
commands when 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.
Dynamic Response Mode
Dynamic status, [ESC] w <n>, can be used to allow the host to sense status changes without
sending repeated inquiry commands. The operation of the dynamic response varies depending on
the configuration of the printer. If the printer is configured for serial or parallel, IEEE 1284
operation, more than one status can be sensed as the printer will respond to status changes as if