Xycom XVME-976/202, Manual

Page: 36 / 87

XVME-976 Adapter Module
2-10
Beyond the choice of I/O base address and interrupt described in the previ-
ous sections, there is only one jumper that affects the parallel port at J3.
This is W20, which controls whether the parallel port will function as a
standard PC/AT printer port (output only) or as a bidirectional data port.
The table below shows how to set this jumper.
Table 2-17. Parallel Port Jumper
Parallel Port Usage W20
PC/AT printer port short
Bi-directional data port short
When W20 is open, the direction of data transmission can be controlled by a
signal (port output enable) applied to pin 26 of connector J3, or pin 1 of
W20. This signal enables data output when low, and data input when high.
Only the eight data lines are affected.
A convenient way to generate the port output enable signal is simply to tie J3
pin 26 to one of the parallel port's output control lines (-STROBE, -
AUTOFD, -INIT, or -SEL IN). Whichever line you use, be sure that your
software controls the line in such a way that you get the data direction you
desire.
There are limitations on the total length of cable that can be driven reliably
by the ports of the board. A full discussion of these limitations is beyond the
scope of this manual. In general terms, the maximum cable length depends
on the data rate, and on the amount of noise and interference in the environ-
ment. However, you will almost always have reliable data transmission if
you observe the following restrictions:
•
Parallel Port: Cable length up to 10 feet
•
RS-232C Serial Port: Cable length up to 50 feet; data rates up to 19.2K
bps
•
RS-485 Serial Port: Cable length up to 4000 feet; data rates up to 57.6K
bps
Specifications
The table below lists the various operational specifications for the SSP
adapter module.
Table 2-18. SSP Specifications
Characteristics Specifications
Power Require-
ments +5V 100mA
(+/- 9V for RS232C generated on board)
Temperature 0 - 65º C
Compatibility Compatible with the XVME-956 expansion scheme and any
CPU modules compatible with that scheme.