If you connect a 1kΩ resistor in series with your multimeter (*1), with your multimeter switched to the 20mA (or equivalent) DC current range, you can measure the ability of a logic circuit to source or sink current. And therefore work out if the voltage on an otherwise unconnected input is due to a ...

For more on the effects of a pull-up resistor connected to stray capacitance, read through the
RC Integrator, RC Waveforms and RC Charging Circuit sections in this tutorial.

Mark

1kΩ is a typical value for a pull-up resistor for use with 74xxx and 74LSxxx plus many other 74 series ICs. 74xxx and 74LSxxx series TTL logic and NMOS chips are typically far better at sinking current than sourcing current on an output pin.

With 74HCxxx and 74HCTxxx series logic, being CMOS, it ...

With schematics of digital systems, my preferences are:
For groups of similar circuits, such as address lines, data lines; use a bus structure. One bus for each different group. With individual lines fanning out to each chip including an appropriate label. This is especially important when mixing ...

Welcome to the China remarking lottery market. Because that’s what it is with popular out of production chips (by this I mean the NMOS versions being out of production).

Chips that have been pulled from old equipment are cleaned up, and then the tops relabelled (remarked). Then they as sold as ‘new ...

Can I just point out that some members here have difficulty reading coloured schematics. It would be appreciated if you can either post black and white diagrams, or provide both.

Also that there is normally no problem with 74HCxxx driving 74HCTxxx. And there is no problem with 74HCTxxx driving ...

And plenty of 100nF capacitors connected close as possible to the VCC/+5V and 0V/GND pins of each chip is also essential.

Mark

Prior to the introduction of electronics to railroad signalling (which was a slow process), a device called a polar relay was used at the receiving end to control different parts of the signal system according to input signal polarity. A polar relay has three states: off, and two on states that ...

I'm not sure if I'm explaining this correctly, but in the past I could run down the pins on an IC socket (or an IC) and make 5 ~ 6 joints quickly and have each be just so before having to clean the iron tip, then a little wipe on a sponge and a dip into the brass wool and I'd be okay for another 5 ...

ISSI definitely did produce 32K byte SRAM in 28 pin skinny DIP/DIL form. I have an old PC motherboard with bunch of them on. See photo…

5EE8E5CD-C6AC-4852-871D-6A7FA6F6F1D5.jpeg

ISSI may be like some other semiconductor companies, in that they only keep datasheets of their current range online ...

Things that I would be thinking about if I owned this J.P. Designs Parallel 65 SBC:

How much it is worth depends on how much people are prepared to pay for it. Not always, but sometimes obscure but rare items can suddenly gain value at some magic point in the future.

I don’t think I would want to ...

For a good solder joint on a through hole board, you need a reasonable soldering iron.

More important than the iron being temperature controlled is the thermal mass of the hot part of the iron (including the tip). The iron and tip must have enough of a heat reserve so that enough heat can flow from ...

I too use a logic probe extensively.

But I also often use 3mm LEDs with suitable resistors soldered to them. The older type of LEDs that have a forward voltage of between 1.8V and 2.2V normally survive reverse polarity on a 5V rail if the current is limited by a resistor.

5B7B8E07-AD25-4A45-B314 ...

Always a good idea to buffer the output if you have a spare gate

Mark

If you have unused EPROM/EEPROM space, it’s better to pad with 0xFF than 0x00 as then it programs quicker. Unless of course you actually need the values stored to be 0x00.

0xFF is the ‘blank’ value that memory addresses in a EPROM/EEPROM go to when erased.

Mark