Front Panel Description; Programmable Resistor Board Description - Stanford Research Systems DS360 Operating Manual And Programming Reference

Front Panel
This section covers schematic FP-1 and FP-2 at the end of this chapter.
Display Board
The front panel display board consists of eight 7 segment displays, 50 discrete LEDs, the
keypad and the spin knob.
The front panel uses a a multiplexed scheme to minimize the number of conductors
required to drive it. The 7 segment displays and LEDs are divided into eight sections,
each driven by a strobe line. All of the displays share a common pull down (Da-Dg, Ddp)
and the LEDs have 7 shared pull downs (LED0-LED6). When a strobe line is hi, that
display is active, with the displayed segments detirmined by the display pulldowns. The
LEDs that share that strobe line are also active, controlled by the LED pulldowns. This is
repeated for each of the strobes in turn.
While a strobe line is high, the keyboard port (KEY0-KEY4) is able to read the keys on
that strobe.
The spin knob is an optical encoder. Each transition of its quadrature outputs is clocked
into circuitry on the digital board. The main processor keeps track of the knobs direction
and speed.
Output Board
The output board provides connections and filtering for the front panel outputs on the
DS360. The + output and - output are brought from the analog board on RG174 cable.
There is additional coupling from the analog board common to the chassis ground on this
board from R1 and C5-C8.
Programmable Resistor Board
This section covers schematic PROGR-1 at the end of this chapter.
This board is a dual programmable resistor. Individule resistors are selected by control
lines R0-R5. Any combination of resistors can be selected (32 possibilities), however
only nine of them are use in the DS360 (R5, R4, R3, R2, R1, R0, R0+R5, R1+R2+R3,
R1+R2+R3+R5). Each half of the circuit is always set to the same value. Two of the
programmable resistor boards are used in each unit.
Circuit Description
DS360 Ultra Low Distortion Function Generator
7-9