Dynamic Shift Registers - Bitsavers - Trailing-Edge

APPENDIXI~oWHAT ABOUT INSTRUMENTSAND CONTROLS?While it is safe to predict that 1970 will be "theyear of the MOS" in alphanumeric terminals, MOSapplications in numeric readouts are just beginningto emerge.A new device with considerable promise in thisfield is a high voltage, MOS static shift register, theMM5081. Developed by National, it has a TTLcompatibleserial input, 10 parallel outputs thatcan stand off -55V, 10 latching-type storagestages, and a serial output.This novel combination of functions means thatthe MM5081 can drive lamps, numeric indicatortubes, filament tubes in segmented number andsymbols displays, electroluminescent panels, andthe new gas-cell arrays. In short, it provides MOSwith a good foothold on the numeric side of thereadout family tree in Figure 1.The register stages can either shift the bits to theserial output for recirculation or store the dataindefinitely. Hence, displayed characters can beswept along a line of indicators, "frozen" on astationary display, or made to reappear periodicallyat any desired repetition rate.A code-converting/character-generating ROM canbe placed at the register input, to display numbersand symbols or alphanumerics. A designer can getalmost as much flexibility from a lamp or paneldisplay as from a CRT display. In fact, the firstapplication of the MM5081 is controlling a matrixof neon lamps in a moving billboard display.Some applications for character generators in instrumentsare also cropping up. Displaying rangescales on an oscilloscope is a good idea that can beimproved upon with the new ROMs_ The displayfrees the operator of the chores of mentally calculatingscale factors and manually writing these onscope photos. With an alphanumeric font, thecamera can also record information such as testconditions, date and time of test, identificationnumbers, etc_ Photo sequences and the dataneeded to analyze the curves can be coordinatedautomatically.Similarly, a ROM can be programmed to displaystandard curves for go-no-go equipment checkoutoperations_ For example, if a radar's pulse amplifiershould have certain output characteristics, theROM generates the correct output curves througha digital-to-analog converter and stroke generator.When an actual operating characteristic and thereference curve are displayed simultaneously, theoperator can tell at a glance whether the radar isfunctioning properly. Many curves or general purposecurve segments can be programmed into aROM and picked out as needed with selectorswitches or a ROM microprogram mer.ROMs can be programmed as lookup tables,random-logic synthesizers,4 encoders, decoders,and microprogrammers as well as character generators.A single ROM can perform limited combinationsof these functions, virtually qualifying it as amicrocomputer. It has been suggested that thiscapability be used in control panels to performfunctions like actuating an alarm when a transducerlevel goes out of range and initiating correctiveaction. ROM addresses can be derived fromdigital meter circuitry. In mUlti-point measuringsystems, this would provide the solid state equivalentof a rack of meter relays.DEFINITIONS OF DISPLAY TERMSFont: A set of printing or display characters of aparticular style and size. A typical dot-characterfont is 5 x 7, referring to the number of dot locationsper character.Dot Character: A character formed by a pattern ofbright dots on a CRT screen or dark spots on hardcopy, rather than by continuous strokes. The dotpattern corresponds to bit-storage patterns in adigital memory.Column: In a dot character matrix for verticalscanning, a column is a vertical series of dots_ On apage display, a column contains several verticallyaligned characters. In this article, a column refersto a dot column.Row: A horizontally aligned group of characterson a display.Line: In this report, line refers to the number ofdots displayed in a single scan when a raster scancharacter is generated. In a 5 x 7 dot character,there are seven lines of 5 dots each.Page: A display consisting of several rows of characters,corresponding to lines on a printed page.Raster Scan: See Figure 9.Vertical Scan: Two types of CRT vertical scans areshown in Figure 10. In hard copy applications, thedots in a column or character may be printedsimultaneously by the printing transducers ratherthan being scanned.Sawtooth Scan: See Figure 10,Pedestal Scan: See Figure 10.Dynamic Element: A digital device that must beclocked. A dynamic shift register must be clockedto retain data. A dynamic ROM is clocked todecode the address and generate an output.Static Element: A device that does not have to beclocked to retain data. A static ROM uses directcoupled decoding for bit selection and static outputbuffers.239