Of course the legacy parts largely were fabed in legacy processes, so an additional
challenge to insure device behavior/specs same, if purpose is replacement.
PALs and GALs, there are some modern process/architecture FPGA to handle that,
eg. small logic designs. Even mixed signal with ability to create custom logic/
functions using simple schematic capture and/or Verilog. An example of such a
device (one chip, many resources shown multiples onchip) :
This above standard lib expanded by users doing Verilog/Schematic capture and creating
additional onchip components. Like 24 and 32 but DDS, 74HC style logic elements, CORDIC,
CPLD.....
Users have created single chip oscilloscope with this part, some work I did (64 bit shift register, 64 bit counter) and :
Occasionally I need to generate custom wave forms and burst a known number of cycles into a DUT. This is a single chip solution, board I typically I use is $ 10. You just drag and drop components onto schematic, wire internally with a wire wizard tool and out to pins, right click and config...
Regards Dana.