Digital Logic for Edway Radio Club

10/27/2022

October 13, 2022 Presentation to the Edway Radio Club

Page 1

This presentation is one of well over 20 more in this particular topic, but I will only bore you with this one.

Before we get down to the nitty-gritty of what we need to cover, I should give just a little background of where this is coming from:

With all the technical advances we enjoy today, it's a little difficult to realize what it's taken to get here.

We today think of Digital Logic in terms of the chips that are available, but what about before those, like perhaps assembling little rocks?

We were not that far removed from Relay Logic, etc...,  Transistor Logic was new with -6V and PNP circuitry!  Try and research that.

Our I/O Device          Note the 5-Level "Baudot" Code, not Hexadecimal.

"Star Finder"    Programmed with"Punched-Paper-Tape", for the Mission.

Page 2

* Among other things, I had been an Instructor at Boeing’s Commercial Training Division for a while.

* Later, I was transferred to the brand new Space Center, where we had the largest Space Chamber in the world.

* I was there when the Lunar Orbiter was tested on the Shaker Tables and in the Space Chamber, and the Moon Buggy was tested as well.

* Using only Analog Techniques, we analyzed missile telemetry for the amount of energy at different frequencies, to test those effects on missile payloads, using the Shaker-Pot platforms.

* This is when management decided to open some new technology with a High Speed Computer system, allowing us to Digitize the telemetry. (~1968-1969)

We had one of Only 2 A/D units in the world, with 320K samples per second, with an accuracy of  +/- 2mv, over a range of -2V to +2V.

* While being responsible for maintenance on our new Digital System, and I was writing diagnostics for all the support peripherals, 

- - and creating a couple of new Operating Systems for the new SIGMA II Mainframe (all in Machine Code).

* The SDS-910 was used to manage the liquid Nitrogen coils in the Space Chamber along with controlling the Solar Hood, to simulate heat from the sun.

* Scientific Data Systems (SDS) and SIGMA had joined companies. The SIGMA II and the SIGMA 7 were newly released together.

* I was called back to the Industrial Training Center to be assigned to teach theAWACS Technicians about Digital and Computer Concepts.

AWACS First Flight: May 25, 1976 (E-3A with full mission avionics)    https://en.wikipedia.org/wiki/Boeing_E-3_Sentry

* I had 2 weeks with each of the 3 work shifts of the Techs that worked with the Westinghouse Engineers, taking them from absolute zero to fluency, with what they could understand immediately, remember and apply.

* To the best of my knowledge, some of the methods and techniques presented here, are not in the textbooks even today.

Page 3

* This is when management decided to open some new technology with a High Speed Computer system, allowing us to Digitize the telemetry. (~1968-1969)

For a Digitizer, we had one of Only 2 A/D units in the world, with 320K samples per second, with an accuracy of ±2mv over a range of -2V to +2V.

* While being responsible for maintenance on our new Digital System, and I was writing diagnostics in machine code for all the support peripherals, and creating a couple of new Operating Systems for the new SIGMA II Mainframe (also in Machine Code).

* The SDS-910 was used to manage the liquid Nitrogen coils in the Space Chamber along with controlling the Solar Hood, to simulate heat from the sun.

* Scientific Data Systems (SDS) and SIGMA had earlier joined companies. The SIGMA II and the SIGMA 7 were newly released together.

* I was called back to the Industrial Training Center to be assigned to teach theAWACS Techniciansabout Digital and Computer Concepts.

* I had 2 weeks with each of the 3 work shifts of the Techs that worked with the Westinghouse Engineers, taking them from absolute zero to fluency, with what they could understand immediately, remember and apply.

* To the best of my knowledge, some of the methods and techniques presented at that time, are not yet in the textbooks even today.

AWACS First Flight: May 25, 1976 (E-3A with full mission avionics)  https://en.wikipedia.org/wiki/Boeing_E-3_Sentry

Page 4

Now,I want to focus what is needed to understand and pass the questions in Element #4 for the General Class and Element #5 for the Extra Class

The first thing to address is the use of "Truth Tables", using "Mil-Spec Logic Sysmbols", and are taught everywhere at the beginning, they are useful for proving a point, and you need to expect them during test time, but in the real world of design, analysis, or troubleshooting, they are totally useless !!  I'll show you what I mean...

Basic Gates & Truth Table s     Now, we get serious:      Gates vs Functions

{ Think "Function" not the "Device" , "Only" vs "Any","Forced" vs "Maybe", "Kill the Gate",  "Slide the Inverter", "Transform the Gate", Multiple Inputs }

Always Design by Function, then find a Device to do the Task.

The "Cross-Coupled NAND", and other scaled devices  (SSI, MSI, LSI) with Preset (Set) and Reset (Clear) Inputs.

Illustrations for "Gate-Transforming"        (10/27/2022)

Two Dual-Input NANDs feeding a third NAND

Two Dual-Input NANDs feeding a NOR

Two Dual-Input NORs feeding a third NOR

Two Dual-Input NORs feeding a NAND

Page 5

Other considerations for "Dynamic Signal Analysis":

• "Coincident Signal Gating", "Enable" vs "Inhibit", "Combo", Tri-State, Multiplexing (MUX)  vs De_Mux, Data-Latch vs Transparent D-Latch, J-K Flip-Flops,
• Master-Slave J-K Flip-Flops, Data-Selectors, Data-Distributers, One-Shots, Re-Triggerable One-Shots, Counters, Synchronous Counters, Decoders,
• Ripple-Shift-Registers, Synchronous-Shift-Registers, Static Memory, Dynamic Memory, Display_Drivers, Programable I/O Devices, Signal-Conversion-Devices.

“We don’t know what we don’t know”