Vector Graphic Bitstreamer II, Руководство пользователя

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connected to the board may send +12 VDC on one or more lines, most often
RS-232C lines 4 and/or 20. You do not have to nonitor these lines,
necessarily. If you choose to, you can connect one or
~NO
of these lines to
the 8251 via an RS-232C line receiver. The 8251 has t..-;o pins that can be
used to receive handshaking signals: pin 17
(eTE")
and pin 22 (DSR).
Software can monitor the status of DSR by monitoring ~~e appropriate bit in
~~e 8251 status byte. The RS-232C line receiver 12 VDC to make this
bit a binary 1 (ON). Software cannot monitor the
ers
status. Rather, if
the input to
ers
is OFF, the 8251 will not transmit anythin3. Sof t',ya re can
tell that the 8251 is ready to transmit by monitoring the TxRDY bit in the
status byte, or by being interrupted by the TxRDY 8251 output (pin 15). For
information on the 8251 status byte, refer to one of the 8251 references
mention~j in the Perspective section of ~~is manual.
Detailed instructions for installing the appropriate jumpers and chips
(if necessary) follow:
Most RS-232C handshaking lines are available on the board, as shovm by
Table 3, in jumper areas H, I, or
J
(depending on which channel you are
connecting to). 8251 pins 17, 22, 23, and 24 are available in jumper areas
N,
0,
or P (depending on which channel you are connectin'3 to.) For
convenience, Table 4 below lists the jumper areas associated with each of
the serial channels:
16-pin Connector
Socket
I/O Jumper
Area
8251 Jwuper
Area
Direction
from 8251
In
In
Out
OUt