PALs and 2023

Hi,

74LS is obsolete, there are other logic families that might suit you more. 

In any case, the (slightly more) modern replacement for typical PAL chips were CPLDs. They are also now not as common, but there are plenty for sale on Farnell/Newark, so if this is a hobby project, then CPLD could still be a suitable option. They are easy to use (either by using a more normal HDL (Hardware description language; like VHDL) than early programmable logic used (which were more like a text description of table entries), or by directly entering in logic gates into a schematic). 

A nice CPLD family is Xilinx Coolrunner, e.g. XC2C64A, there are hundreds of them in stock according to the Farnell site, and they cost about £10 each (not cheap, but for a hobby project there's often not a requirement for least cost). The required software is Xilinx WebPACK, which is still available from the manufacturer website. The chip comes in TQFP package, but some are very large (0.8mm pin spacing) and easy to solder onto a breakout board using a normal soldering iron. They can be programmed using (say) a raspberry pi, hooked up to the programming pins (called JTAG).

However, the next step up from CPLD is to use an FPGA. The easiest way to get going with them is to first buy a dev board since that may contain a programmer built-in, and easy to use connectors (most FPGAs are finer pitch parts than the old CPLDs), and then when you're happy, you could move to the individual IC. A lowish-cost dev board is ICE40HX1K-STICK-EVN (£49 GBP, currently 99 in stock on the Farnell website). The basic FPGAs such as that are not much harder to use than the CPLDs, but depending on the manufacturer free supplied software they might not come with a schematic entry method, you may have to use a HDL. There is also open source software but that's another topic altogether, and is not applicable for all HDLs. FPGAs take their configuration from external memory by the way, unlike CPLDs.

Yet another approach could be to consider something like Infineon/Cypress PSoC chips or dev boards, they are a microcontroller with a (very tiny) bit of programmable logic attached. However I know nothing about those, and cannot comment.

Infineon PSoCs can be used strictly as programmable logic gates and "TTL" style logic functions without dealing with the MCU at all. They even have comparators and opamps. They can also operate from below 2V to over 5V.

I did an example of PSOC programmable logic without MCU here:

 The Logical Project 

Nice! I'll have to have closer look at your project and associated videos.

The fourth video in that blog shows how you can create logic circuits just by dragging logic gates onto a schematic page. No programming necessary. I think it is the easiest way to implement logic and it is very low cost. You could also easily implement more complex circuits by dragging peripheral function blocks into the schematic - such as UARTS, or if you want to generate a clock at a specific frequency - just type in the value to a clock module. (a simple way to test your 6809 running at different clock frequencies) It could probably even act as the RAM for your project although the part I used only has 2K or 4K.

The fourth video in that blog shows how you can create logic circuits just by dragging logic gates onto a schematic page. No programming necessary. I think it is the easiest way to implement logic and it is very low cost. You could also easily implement more complex circuits by dragging peripheral function blocks into the schematic - such as UARTS, or if you want to generate a clock at a specific frequency - just type in the value to a clock module. (a simple way to test your 6809 running at different clock frequencies) It could probably even act as the RAM for your project although the part I used only has 2K or 4K.