8
PRS Series
BCD INTERFACE OPTION
Chapter 4
BCD INTERFACE OPTION
4.1 BCD Programming
PRS units, with BCD interface option, come with a
BCD (Binary Coded Decimal, 1-2-4-8 coding) re-
mote programming capability accessed through the
BCD INPUT connector
The connector is a 50-pin, female, parallel-interface
industry-standard connector found on the rear panel.
Table 4.1 shows the connector pin numbering . Table
4.2 gives the pin assignments for the BCD input for
this connector. There can be as many as 10 digits to
be input. For any unit with fewer than 10 digits, only
the implemented subset of these will be operational.
All other digits may be ignored, and the associated
pins may be left open or shorted to ground.
Once the unit is switched to REMOTE with the front
panel knob, it may be set to either LOCAL or RE-
MOTE states under external control by properly se-
lecting pins 21 and 22 on the BCD INPUT rear panel
connector as shown in Table 4.1. Note that both pins
must be set. The REMOTE and LOCAL led’s will
respond accordingly. Once the PRS is set to Re-
mote, the thumbwheel switches become disabled, and
impedance control is transferred to the rear panel
connector.
In addition, two special optional function pins are pro-
vided to set the unit to Open-circuit or (optional) Short-
circuit states across the HI and LO terminals on the
front panel. Applying a low to pin 34 activates an
open circuit condition. If the short circuit option is
present (this option provides a lower resistance short
circuit than a zero setting), applying a high to pin 35
provides a short circuit. If these functions are not
required, these two pins may be left open, or the op-
posite logic levels may be applied, i.e. high to pin 34
and low to pin 35. If both pins are activated, the
system will be in the short-circuit mode. If the short-
circuit option is not present, pin 20 may be left in any
state.
Table 4.1 BCD INPUT Connector
(Viewed from rear of instrument)
25
24
…………….
2
1
50
49
…………….
27
26
