[Color Computer] Re: [Coco] Motorheads and the CoCo...
jdiffendaffer at yahoo.com
Wed Jun 15 20:09:16 EDT 2005
I'm pretty certain the 68HC11 has been used for this purpose in the
past but I'm not sure what clock speed. Probably a little faster than
the 09s that are out there. For some reason I seem to remember it
being over 10MHz (16?) but I don't even know if that chip is available
in that speed.
I think manufacturers have long since moved on to chips like the 52
series Coldfire CPUs and various RISC chips. The ignition and fuel
mapping is much more complex than it used to be and that requires
greater speed and a larger address buss to handle the data.
--- In ColorComputer at yahoogroups.com, "George Ramsower" <yahoo at d...>
> Taxing the coco is a major concern with an SEFI system. So in my
plans, the coco does not actually do all the work. It only handles
engine management, while a separate board will actually do all the
actual work of firing injectors(PWM), adjusting the idle air bleed
stepper and controlling spark advance.
> The coco will monitor MAP, MAF, O2 sensor, coolant temp, air temp,
RPM and all the other required information to make the commands to the
> My thinking is that if the coco fails, crashes or otherwise is
rendered inoperable, the controller will still function and run the
engine in the "Limp Home Mode".
> The rough drawings and parts list for the controller is not simple
in any way. It is totally constructed using standard old TTL chips
mostly, some other chips that do stuff like the PWM for the injectors,
up/down counters and a lot of 555 timers. It will have 64K of static
RAM also for mapping the RPM range and TPOS and MAP.
> The mapped static RAM is preprogrammed by the coco after initial
power is applied to the controller.
> Too much to tell about this in one email.
> I believe that the coco is fully capable of handling the
management end of this system, even if it was written in RS-Basic..
but I'll use OS-9 because I like it.
> Since the coco will have to load up software to do this, the
controller will work fine during initial startup of the engine. Once
the coco is online with things, it will make any necessary adjustment
to the controller while the vehicle is in operation.
> The reason I decided to use the old reliable 74XX and 74xxx, some
54x stuff to is speed and reliability. TTL is equal to about five
million instruction per second. More than is necessary to control an
engine at 6000 RPM(one hundred revs/second). Since 4-cycle engine
timing is based on the camshaft in SEFI, we now are dealing with only
> Okay, some of you have engines that are good to 7500 RPM. This is
still only 62.5 turns/sec on the cam.
> Surely this could be done easily with something like a 68hc11 or
some of the other magnificent microcontroller chips, but I'm crazy
about the old TTL stuff and using a coco to control them.
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