Memory Array - Page 1
Forum section: electronics / beginners

author: SurprisingRice
author_rank: Newbie
timestamp: July 22, 2015, 02:50:40 pm
content: Is it possible to create a memory array using only diode transistor logic?(sorry if its a noob question)

author: Zero999
author_rank: Super Contributor
timestamp: July 22, 2015, 03:06:17 pm
content: Yes.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 23, 2015, 11:43:59 pm
content: Yes, they called that DTL (Diode Transistor Logic) and it was used before memory ICs were created. Use two transistors to create a bi-stable oscillator and use one or two inputs to set it or reset it. The output is obtained from one of the two transistors. In computer terms it's called a DS (Direct Set) Flip Flop and you have to make a complete circuit for every memory bit. They also made JK Flip Flops and (IIRC!) RS Flip Flops. You can even build the same circuits with vacuum tubes if you desire.

author: Mr.B
author_rank: Unknown
timestamp: July 23, 2015, 11:56:48 pm
content: Quote from: Stray Electron on July 23, 2015, 11:43:59 pmGoogleSelectron tubeMakes for interesting reading.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 24, 2015, 08:09:51 pm
content: Quote from: Mr.B on July 23, 2015, 11:56:48 pmYes, interesting reading!"Development of Selectron started in 1946 at the behest ofJohn von Neumann"How many here know who he was?

author: German_EE
author_rank: Super Contributor
timestamp: July 25, 2015, 06:55:51 am
content: Quote from: Stray Electron on July 24, 2015, 08:09:51 pmIn Budapest close to the West End Shopping Centre there's a street where he used to live and someone has put a plaque on the wall of the building. I wish I could remember the name of the street

author: mikerj
author_rank: Super Contributor
timestamp: July 25, 2015, 07:38:44 am
content: Quote from: German_EE on July 25, 2015, 06:55:51 amBudapest, District V, Báthory Street Nr 26 according toWikipedia

author: SeanB
author_rank: Super Contributor
timestamp: July 25, 2015, 07:53:29 am
content: Most mask ROM is based on a diode array. You use diodes as elements, and where you want a 1 you put the diode in in the top mask layer. Older computers did this with a massive array of diodes on a board, where you only populated the diodes needed.For small arrays this can work out well, if you want say a 7 segment display of 1 of 10 inputs, where only 1 input at a time will ever be high.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 27, 2015, 04:13:09 pm
content: They did something similar with core memory to create ROM. They inserted a core where they wanted a 1 output and left the core off where they wanted a 0 output. It was referred to an "Core On A Rope" and was used in the Apollo space craft. I had a chance to buy several of them about 15 years ago but didn't do it.Part of the description from Wikipedia?"Core rope memory is a form of read-only memory (ROM) for computers, first used in the 1960s by early NASA Mars probes and then in the Apollo Guidance Computer (AGC) designed and programmed by the MIT Instrumentation Lab and built by Raytheon.Contrary to ordinary coincident-current magnetic-core memory, which was used for RAM at the time, the ferrite cores in a core rope are just used as transformers. The signal from a word line wire passing through a given core is coupled to the bit line wire and interpreted as a binary "one" while a word line wire that bypasses the core is not coupled to the bit line wire and is read as a "zero". In the AGC, up to 64 wires could be passed through a single core."

author: C
author_rank: Super Contributor
timestamp: July 27, 2015, 07:53:44 pm
content: Quote from: SeanB on July 25, 2015, 07:53:29 amThere was a programmable rom that started with all diodes in place and the programing step was to blow the diodes not wanted.Quote from: SeanB on July 25, 2015, 07:53:29 amWorked with a version that had all the diodes on board and you cut or added jumpers. Some replaced the jumpers with a switch.C