[sdiy] 8253 modern replacement?

rsdio at audiobanshee.com rsdio at audiobanshee.com
Fri May 8 19:01:00 CEST 2015


In the 80s, peripheral functions were almost always additional chips added outside the main processor. These days, almost every kind of peripheral you might want is already included inside the processor. Sometimes call a System On Chip (SoC), modern processor typically have several timers like the 3 in the 8253.

Note that a few PIC or other chips might have some timers that are only 8-bit, while others can operate as 8-bit or 16-bit. There also might be limitation on which timers have external pins for output, versus being restricted to internal interrupts only. These new timers usually have multiple options for input clocks, and some even allow a separate crystal as a dedicated input in case you need frequencies that aren't a multiple of your processor clock.

This thread has already mentioned PIC and AVR, but don't forget that other options like MSP430 and ARM also have built-in timers. Some of these chips even have 5 or 6 internal timers. If you want more than 6 independent DCOs, you might want to consider discrete logic or an FPGA. As Roman discovered, you can sometimes end up with a huge circuit if you try to implement every feature, but there might be a shortcut you can take (e.g. if you don't need to read the timer count). An FPGA will allow you to squeeze several timers and interfacing into a single chip, but it might be easier to just use a couple of standard SoC parts that each have several timers inside.

Brian Willoughby
Sound Consulting


On May 8, 2015, at 6:12 AM, Jack Jackson <jackdamery at hotmail.co.uk> wrote:
> The 8253 programmable interval timer IC was used a lot in the 80s for generating frequencies for DCOs. Is there an easier way to do this in modern times? Maybe a modern IC with a smaller footprint or something else entirely?
> 



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