86
MULTIPORT SPOOLER VIII (4-, 8-, and 12-Port Models)
The LED of a bidirectional serial port used as an output port starts flashing
for no apparent reason.
Cause:
Some serial printers use X-ON/X-OFF software flow control to
control the flow of data into their small on-board buffer. If the
Multiport Spooler VIII has DTR/CTS hardware flow control
enabled, it will think that the X-ON/X-OFF characters sent
back to it by the printer are data characters.
Solution:
Change the configuration of the Multiport Spooler VIII’s
bidirectional serial port where the printer is connected to
that of a serial output port.
NOTE
DTR/CTS hardware flow control is the only type of flow control supported
by DOS and all applications that use DOS to print.
There are problems printing or plotting from AutoCAD.
Background: AutoCAD drivers for serial plotters usually have fixed serial
communication parameters: 7 data bits, even parity, and
1 stop bit. (Only the number of data bits and the parity are
relevant to this problem.) For example, let’s consider the
following PC—MPS-VIII—Plotter installation:
The PC is connected through its serial port to one of the
Multiport Spooler VIII’s serial ports. The plotter is connected
to a different MPS-VIII port. The PC’s serial port, the MPS-
VIII’s two serial ports, and the plotter’s serial port are all
configured to match the fixed AutoCAD configuration of 7
data bits and even parity. Plot data is sent from the PC through
the MPS-VIII to the plotter.
In this sort of arrangement, the following problems can arise.
Cause 1:
Word-processing software is installed on your PC and its ouput
is sent to a printer. The printer is connected to one of the
Multiport Spooler VIII’s parallel output ports. You plan to use
the existing serial connection on your PC to send AutoCAD
output to the plotter and word-processor output to the printer.
Furthermore, it might be useful to send AutoCAD output to
the printer. So you use the UCTP to send port-redirection
commands to the MPS-VIII for switching between the plotter
and printer. Everything looks good on paper, but it just doesn’t
work in practice.
Содержание PI750A
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