Jon Elson wrote: > Sebastian Kuzminsky wrote: >> A typical EPP transaction for this driver consists of two address cycles >> and 16 data cycles, for a total of about 20 or 25 microseconds of no >> interrupts. It occasionally (rarely) spikes as high as 75 microseconds. >> >> There's a judgement call here, and I seek your advice. Is 25 >> microseconds too long to run with interrupts off? > > Memory refresh is usually done by interrupt, and you don't want > to delay that too much. What happens if the EPP bus hangs? > 20-25 uS could turn into hundreds of us if the driver doesn't > have some abort strategy when it gets an EPP timeout (which > should never happen, but plug falling out, slave board losing > power, etc. could cause it)
The driver detects EPP timeouts and handles it gracefully. I started out my development with a *bad* EPP cable, so this was a code path that got much exercise! But yes, good point, timeouts would likely push the 75 us observed worst-case much higher. -- Sebastian Kuzminsky Cryogenic travel has improved since then... I woke screaming in a translucent box. “There, there,” said the box. “Everything will be all right. Have some coffee.” -- Ken Macleod, "Who's afraid of Wolf 359" <http://outofthiseos.typepad.com/blog/files/KenMacleodWhosAfraidofWolf359.htm> ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
