Nice to hear you again. Since I want to extend interrupt sources and only want use one 8051, but the 8259 is one of my choices. Do you have any suggestions? Best regards.
stay away from 82xx chips. Possible solutions a (C)PLD a simple or gate if the interrupt sources are latched externally and the ISR reset the latch more exist, just visualize Erik
I'd like to know what is the reason to stay away from 82xx chips.
I'd like to know what is the reason to stay away from 82xx chips. OK, here are a few I can think of right off the bat, I am sure there are more, but the "no more 82xx" happened ten or more years ago, so my memory may be a bit rusty. Anyhow, the deciding factor whatever it was - was an absolute. *They are designed for the x86 and thus the interface is bad for a '51 *They are, in may cases, too slow for a modern '51 derivative to drive as MMIO *The only place you can buy them is an antique store *They ususally require external logic to be interfaced to a '51 *Everything we used a 82xx for, in the olden days, can now be done better, cheaper, and safer using other means. Erik
Since I want to extend interrupt sources and only want use one 8051 An interrupt expander, whatever the type, is usually a bad choice (in a '51 environment). where can you get more interrupts? * every timer can be made an external interrupt. * every comparator, with interrupt associated, can be used as a logical interrupt. * A PCA can give you 5 additional external interrupts. * and A/D with limit interrupts, can be used as a locical interrupt. So, whith something like a SILabs F12x you can have about 15 external interrupts. an example of converting an interrupt to "external": configure a timer as a counter, load it with ffff and the very first clock on the input pin gives an interrupt. Erik
"I'd like to know what is the reason to stay away from 82xx chips." Did you want just the 5-minute list, or the full half hour...? ;-) http://www.8052.com/forum/read.phtml?id=81257 If you really want to use an obsolete chip, you could at least use a modern one - and choose a Triscend E5! Anyhow, there are plenty of 8051s available today with tons of IO built-in. So why would you choose a variant with insufficient IO and then add an inappropriate, obsolete part to increase it to the required IO?! Makes no sense! You'll be telling us you've found this box of thermionic valves ("tubes") next, and how can you interface them to an 8051...
an added comment The main reason that you still see 82xx in use is that many authors of "reference designs" or "demo boards" are simply too lazy to redesign their antique stuff. Selling a thing you made 10 or more years ago, is pure profit, making a contemporary design require effort. Erik