Measurement Computing Serial488/4 - Manual (Page 23)

Section 2 Getting Started
2.11
2.5.1 RS-232/422 Configuration Jumpers
Each serial port is capable of operating w ith either RS-232 or RS-422
electrical characteristics. This selection is done via a set of hardw are
jumpers located on the main board behind each serial connector. A twelve
position jumper plug must be inserted in one of the two available positions
for proper operation. These jumpers are factory set to configure all ports for
RS-232 levels as illustrated in figure 2.7.
If configured for RS-422, each port's Receive Data (RxD) and Clear to
Send (CTS) input lines may optionally be terminated with a 100 ohm
resister. Termination resisters are selected by positioning the two flea clips
located behind each serial connector tow ards the front panel, or upper
position. T hese jumpers are factory set
to the unterminated position,
towards the rear panel. The jumpers associated with each port are: port 1
JP104 &JP105, port 2 JP109 & JP110, port 3 JP114 & JP115, and port 4
JP119 & JP120.
Figure 2.8 illustrates port 1 jumpered in RS-232, RS-422
unterminated, and RS-422 terminated with 100 ohm resister (left to right).
NOTE: When using RS-422 in a single ended configuration ports must be
unterminated for proper operation.
NOTE: Termination jumpers have no effect w hen ports are configured for
RS-232 operation.
WARNING
Never open the Serial488/4 case while it is connected
to the AC line. Internal voltage potentials exist which
could cause personal injury or death.
To open the Serial488/4 place it on a flat surface then remove the four
screws on top of the case and remove the top cover. Located in front of
the four serial port connectors,
are four sets of connectors w ith
configuration jumpers, one set per serial port.