18F26K80 Serial setting sanity check and 4xPLL.

[Acetronics2]

Hi, Peter

does not your oscillator run or does not your program work as expected ??? Here is THE big question ...

80 Mhz looks to be "reachable" ( with careful design ... ) with Pics but, as PBP "timed " commands are not available for more than 64Mhz clocking, some commands in your program can't work properly ... ( assembler Ghost in sight !!! )

sooo, to me, it's no use to go on the " overclocking way " ... without using some assembler.

Sorry ... Even I do love Hondas ( mine is a 2020 Civic 4D 1.5L CVT ... and I Have Driven only Hondas for ... 32 Years ! )

Alain

[retepsnikrep]

I will revisit all the replies. Thanks

[retepsnikrep]

I have the PIC running at 80 and 96mhz on the bench now.
Looks like it was a setting issue and not waiting for clock to settle before engaging PLL.
Thanks for the ideas/help.

[tumbleweed]

Great.

Keep us posted on how it goes. I'd be interested to know if you have any problems with peripherals operating at those speeds, esp the builtin CAN controller.

[retepsnikrep]

I also had a bad/fake 20mhz resonator.

I then tried some Farnell ones and decent crystals all worked ok, even at 96mhz.

The board actually worked in the car at 96mhz but that is overspec (12mhz) for the 10mhz MCP2515 CAN controllers SPI so I dialled the PIC back to 80mhz for reliability and (10mhz SPI)

So a decent increase in speed over 64mhz at zero cost so far.

Now back to the other thread to do some code speed optimisation before I add additional functionality with my extra free time.

[HenrikOlsson]

I'll admit, I've been sceptical about relying on overclocking for something that is actually being used but I suppose if it works at 96MHz(!) then dialing it back to 80MHz does provide some margin.
Since it's going to end up in a car I'd probably test it at something other than room temperature before banking on the extra instruction cycles. I know you said it did work in the car at 96MHz but at what temperature?

Looking forward to the optimisation thread!

[retepsnikrep]

To be fair it worked ok at 64mhz without any optimisation I'm just being greedy and trying to free up/gain some cycles in advance of other stuff.
I have a heat gun and freeze spray so it's pretty easy to stress it.

It's been working fine in the summer sun for last two days at 80mhz.
30-35C in the car.