Timeline for First TTL chip in space and in orbit? Was it a 7400 series or something that predates?
Current License: CC BY-SA 4.0
14 events
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| Jul 14, 2021 at 15:33 | comment | added | supercat | @Uwe: Power and ground pins are only inputs and outputs if a device is intended to respond to changes in the power that's available to a device, or control the flow of current to other devices. As for the "rule", it's a guideline which is followed when there is no compelling reason to favor one direction over the other, but which often gives way to other considerations. | |
| Jul 14, 2021 at 14:57 | comment | added | Uwe | @supercat Swap pins 10 and 1 on the left side would be a violation of the rule: outputs to the right! Readability of the schematics is much better when those rules are followed as strict as possible. Pin 5 and 10 exist only one time for both gates, so it is possible to draw those pins on one side only. | |
| Jul 14, 2021 at 14:40 | comment | added | supercat | @Uwe: Swapping pins 10 and 1 on the left side to match the physical orientation and extending the common-emitter wire on the right side leftward would have allowed the two pin-10 connections to be adjacent, and likewise the two pin-1 connections, even if all the transistor orientations were left alone. | |
| Jul 14, 2021 at 14:00 | comment | added | Uwe | @DrSheldon There is a convention for drawing circuits: inputs and transistor base to the left, outputs and transistor emitter and collector to the right. If symmetric circuits like current mirror or this flip flop are drawn, inputs may be drawn to the right too. But when a flip flop is drawn using gates symbols like the NAND latch, the NOR latch or the AND - OR latch, all inputs are drawn to the left, see [flip flop](en.wikipedia.org/wiki/Flip-flop_(electronics). | |
| Jul 14, 2021 at 12:52 | comment | added | DrSheldon | @Uwe: I meant the way that they drew it is non-symmetrical, not the actual pinout. | |
| Jul 14, 2021 at 9:00 | comment | added | Uwe | @DrSheldon For a really odd pinout look for 74LS273 compared to 74LS373. If they would have done it right in the first try, there would be no 74LS273 at all. | |
| Jul 14, 2021 at 8:55 | comment | added | Uwe | @supercat and @ DrSheldon Pinout was not that odd. It should be possible to use the gate as a NOR gate with two inputs by grounding an unused input. Connecting pin 4 to pin 5 GND was easy using adjacent pins, same with pin 6 to 5. If an inverter was needed, the pins 3, 4 and 5 were connected. A noninverting buffer was achieved by connecting pin 2 to 9 and ground all unused inputs by a connection of pins 3, 4, 5, 6 and 7. The pinout should avoid additional metallization layers on the chip and additional vias or wire bridges on the printed circuit boards. | |
| Jul 13, 2021 at 21:12 | comment | added | DrSheldon | @supercat: It is rather odd. They could have done a better job conveying the symmetry of the chip. The power pins (5 and 10) should appear only once, and connect the two sides. | |
| Jul 13, 2021 at 19:43 | history | edited | Uwe | CC BY-SA 4.0 |
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| Jul 13, 2021 at 17:37 | comment | added | supercat | @DrSheldon: I wonder why the schematic is drawn with the pins in that order? If one were to draw the schematic with pins in order 10-1-2-3-4-5 counter-clockwise on the left side, and 5-6-7-8-9-10 on the right, the pinout would make a lot more sense. | |
| Jul 13, 2021 at 9:24 | history | edited | Uwe | CC BY-SA 4.0 |
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| Jul 13, 2021 at 1:28 | comment | added | DrSheldon | Helpful picture: static.righto.com/images/agc-rope/nor-schematic.png | |
| Jul 12, 2021 at 19:49 | history | edited | Uwe | CC BY-SA 4.0 |
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| Jul 12, 2021 at 19:41 | history | answered | Uwe | CC BY-SA 4.0 |
