It's already there - the programming and readout circuitry is already used for parallel programming. So the "only" extra thing needed is a command decoder - but it seems to me to be rather trivial, hence I think not too many chances to spoil it.

And don't forget, the UART-ISP DOES involve extra circuitry - that one which is used for the ISP invocation; and indeed it has become a major issue for UART-ISP (see the "lost bootvector" case, whatever is the cause of "loss", the result is a defunct chip (*)).


Craig, you are speaking from the viewpoint of the user, whereas I am speaking from the viewpoint of the manufacturer. From this point of view, the SPI-ISP is simpler and safer in many respects. Of course, the manufacturers standpoint is (or should be), that the user should use a proper programmer, as he would use for parallel programming (here comes the kitchenware-problem).

Don't get me wrong, I am not advocating the SPI-ISP approach. I in fact like the UART-ISP, but not for it's better, safer, simpler, or anything; but for it can be modified by the user - if it's not wired in some obscure ROM - I don't like that variety - and I also don't like the other variety, if it IS in a FLASH and CAN be upgraded, but the manufacturer DOES NOT mention even the possibility of it (and what even publishing the reprogramming details).


Oh yes, that's a good point. Rather, it ought to be debugged. Search the fora worldwide; you will find at least as many complaints on UART-ISP as on SPI-ISP. And, obviously, they are NOT caused by improper "cable"... so what, then?

Jan Waclawek


(*) don't catch me by words: can be recovered by parallel programmer - if one has any