Comment by timthorn
2 days ago
Sounds like a PLD might suit your usecase? Simpler than an FPGA, programmed like an EEPROM, perfect for glue logic.
2 days ago
Sounds like a PLD might suit your usecase? Simpler than an FPGA, programmed like an EEPROM, perfect for glue logic.
I wish CPLDs were more well known in the common vernacular.
The industry draws a distinction between CPLDs and FPGAs, and rightly so, but most "Arduino-level" hobbyists think "I want something I can program so that it acts like such-and-such a circuit, I know, I need an FPGA!" when what they probably want is what the professional world would call a CPLD - and the distinction in terminology between the two does more to confuse than to clarify.
I don't know how to fix this; it'd be lovely if the two followed convergent paths, with FPGAs gaining on-board storage and the line between them blurring. Or maybe we need a common term that encompasses both. ("Programmable logic device" is technically that, but no-one knows that.)
Anyway. CPLDs are neat.
I don’t see how CPLDs solve anything?
You write RTL for them just like you do for FPGAs, you need to configure them as well. The only major benefit is that they don’t have a delay between power up and logic active? But that’s not something that would make a difference for most people.
CPLDs are also a dying breed and being replaced with FPGAs that have parallel on-board flash to allow fast configuration after power up. (e.g. MAX10)
I don’t know anything about this (other than doing mediocre in some undergrad Verilog classes one million years ago). Wikipedia seems to call FPGAs a type of PLD. Of course, everybody has heard of FPGAs; is it right to think they’ve sort of branched off, become their own thing, and eclipsed their superset?
"Programmed like an EEPROM" is part of the problem, any system that needs more than one piece of firmware to be wrangled during the assembly/bringup process is asking for pain.
But, really, no one cares what's inside the box. CPLD or FPGA, they're all about the same. The available PLDs are still not really acceptable. There's a bunch of 5V dinosaurs that the manufacturers would obviously love to axe, and a few tiny little micro-BGA things where you've got to be buying 100k to even submit a documentation bug report. Not much for stuff in the middle.