6502.org

That seems rather less convenient. LEDs seem like less hassle in that case; the output of a 14495 could be buffered by a 74HC driver and a resistor pack, assuming it at least produces correct levels at 3.3V supply.

Another compact option for 5V people might be the ICM7218 series - though this is one chip that *won't* work down at 3.3V where I want it, it *does* come in a conventional PDIP package and remains in current production. It seems like a good option for "viewer friendly interface" displays that need to be big, bright and drop-dead simple, since it can be interfaced directly between the 6502 bus and the LED modules.

It comes in four variants: A and B are designed for driving via software with maximum flexibility, while C and D have more direct access for use with simpler input hardware; one of each pair is set up for common-anode versus common-cathode LED modules. Both have built-in multiplexing and latches for 8 digits, complete with an internal oscillator, and can decode nybbles as either hexadecimal or "Mode B". External memories and counters can be interfaced to it via the digit-common signals it emits, an 8-to-3 encoder and minimal extras.

Nice! And Digikey stocks each of the four variants in both DIP and PLCC.

Yes, nice - but a wee bit pricey. I guess if you need them, you need them. Market economics at work.

Any microcontroller with a proper number of pins may sample the uP bus state and drive either a multiplexed LED display or a character LCD. The whole stuff would cost < 5 USD in hardware plus some time spent on programming.

Yea, there's something to be said that you can get a Raspberry Pi Zero cheaper than one of these chips.

Hello,

Maybe this will help?
It's not mine, but I did find it somewhere.
Build it with 14 segment displays and it works quite well.

BR/
Guus

For this kind of bit-bashing the Teensy 3.5 board is worth considering: DIP format, ARM, USB programmable, and 5V tolerant. At £24 or $24 it's more expensive than a Pi, and it's less powerful, but that 5V tolerance saves making up a level shifter.
http://www.hobbytronics.co.uk/teensy-v35

STM32 Nucleo-64 boards cost ca. USD 11, 90% pins are 5V-tolerant. BluePill costs USD 1.7, over 20 5 V tolerant pins. Chinese STM32F407VET board (over 100 pins) is USD 9.

We've got plenty of choices when it comes to implementing any retro computer logic in a microcontroller. Note that all these have USB interfaces, which may be used for controlling the device from a PC (status display, loading HEX files to memory etc.). That's what I did in my SDC design.

Thanks for the pointers!

There are some nice little OLED displays (0.91" 128x32, 0.96" 128x64, and 1.3" 128x64) with I2C or SPI interfaces from various sources (including AliExpress) that might be worth checking out.

Here's a pic' of a 0.96" 128x64 I2C OLED display connected to an 8-pin PIC (below). The PIC and the OLED display work well at 3.3 or 5.0 volts.

Cheerful regards, Mike

That looks like more of a graphic display than one that could easily be used to display hex digits, so it doesn't really fit in this thread.

Some info about those displays here:
https://learn.adafruit.com/monochrome-o ... /downloads

It does look likely that they are (only) dot-addressable, so you need to drive them with something which has a font (or several). In Michael's case, presumably the PIC has that, so the PIC could offer a higher level interface or could perhaps even snoop the bus itself.

Huh? I beg your pardon?

I think the goal was to be able to take in four bits per digit, with no selects, no strobes, no latching or registers, just combinatorial logic, like for sniffing the address and data buses when the clock is stopped, and directly drive the display, without having to program anything else. When the computer is not all working yet, it won't be able to drive an SPI or similarly interfaced display. That little graphic display does however look very attractive for other purposes.