TransAct Ithaca 280, Руководство программиста

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Communications iTherm
®
280 Programmer’s Guide
28-04430 Rev K Page 279
be activated. If the printer is placed back on-line while the reverse channel is active, the
printer will not exit the reverse-channel mode.
Inquire Responses
In general, inquire commands place two-byte responses in the IEEE 1284 reverse-
channel buffer. The two bytes are the same as the serial mode responses. In IEEE
1284 mode, the printer remains busy until the inquire command is processed, assuring
responses in real time. To receive the response, the host must ask for it. It is possible
for the host to make a number of requests and wait for the responses; however, the
status returned is valid at the time the request was made.
It is also possible for the dynamic response mode to be activated and the reverse-
channel mode to be opened. The reverse channel then changes from reverse-idle to
reverse-data available as the status changes. The application must be careful in
dynamic response mode that the dynamic responses are not left active when the reverse
channel is closed. If the dynamic responses are active when the reverse channel
closes, the output buffer overflows. If data is in the buffer when dynamic responses are
activated, it will not be replaced by the current status. If dynamic response is off and a
buffer-clear command is issued followed by activation of dynamic responses, the buffer
will contain fresh data. If the buffer-clear command is issued after the dynamic response
is activated, the buffer will be cleared and any unread responses will be lost.
Parallel Port Plug and Play
Microsoft Windows implements Plug and Play (PnP) by doing a special parallel, IEEE
1284 inquire during boot. The iTherm® 280 Printer responds to the inquiry if IEEE 1284
is active.
If the Windows PnP configuration flag is set in the printer, IEEE 1284 will be active for all
parallel-port modes. For example, PnP in parallel mode forces IEEE 1284. For PnP to
work, the host must have an IEEE 1284-compatible port adapter, and the cable used to
connect to the printer must support all of the interface signals.
The Plug and Play response follows.
Device ID string:
Manufacturer:
TransAct.;
CMD:M280CL,IPCL;
CLS:PRINTER;MDL M280 PcOS;
DES:Ithaca M280;
REV:x.xx;OPTS;$9xyz
PnP ID: LPTENUM\Ithaca-Perph.M280_P4D21
Device Description: Ithaca M280
Device Class: Printer
OPTS Field Description
OPTS;$6XYZ