Post by Jon Elson Post by Gene Heskett
What if its actually a group of 82C55's on a pci card thats trying
to look like an ISA card in a pci slot? No bios extensions or any
access support on the card, just I/O and a dipswitch programmable
address decoder. Does this iopl() work for this scenario if the
card is set to respond to $F100 (and up in 4 byte increments)?
Sure. You would use ioperm(0xf100,4,1); to turn on the addresses
from 0xf100 through 0xf103 (4 contiguous bytes). The '1' means to
enable access, a zero would disable access.
Well, since there are 4 addresses per chip and 3 chips, then it would
ioperm(0xf100, 0x30, 0x1);
which would enable access from 0xf100 to 0xf12f. I think the first
chip is at 0xf100-03, for portA, 0xf104-7 for portB, 0xf108-B for
portC, and the mode register then is at 0xf10C-F, repeat the sequence
at 0xf110 for chip 2, and 0xf120 for chip 3. Correct?
Then once this is done, then iopl() comes in to set the priority of
the service up?
What about IRQ's that can also come from an 82C55 in some modes, the
default mode 0 comes to mind. (I think, its been 23 years since I
last fooled with an 8255, from the design something around it
viewpoint, and that was using a Z-80 as the driver, so the memory is
in dire need of a few hundred refresh cycles here)
I've a mind to do, because the cabling for output is a simple 34 pin
ribbon cable for the first 3 axis's, use one chip as all outputs, and
the next chip as all inputs, or at least as many as it will take for
Limit switches: Presumably I'll need a pair of switches for home on
the x/y table, which can be at either end of the table travel, and as
far forward out from under the spindle as the x can safely move
without the leadscrew coming out of the nut.
So 2 microswitches for that are a given. Can the opposite end of the
travel limits be set in a config file, or do these also need
And, since the work piece, unless backed into a cleaned up fixed jig
on the table, is always going to be subjected to how accurately you
can clamp a new piece down when making more than 1 copy, how does one
go about zeroing this error out? But that question is putting the
cart before the horse I haven't bought yet. :-)
I did get the other motor mount made and mounted today, and the
handwheels drilled for the drive pins to engage them, but haven't
made the drive pins and the bar that holds them yet. My shop isn't
heated very well so I had to come in and thaw out my feet after
awhile. Looking at the gearbox innards of these motors, I can see
they will have a fairly low torque limit beyond which the gears will
be damaged, so I'm inclined to do the drive with a piece of steel
strap carrying the drive pins, and just one shouldered bolt into the
center of the sleeve thats setscrewed to the motor shaft, with a
bellvue washer for a breakaway slip clutch. At least it sounds like
a plan for right now.
For the z motion, I think the best thing I can do is ream out the
shaft hole for the drive pinion axle about 1/8" all around, and make
an eccentric bushing so the rack/pinion play can be adjusted down to
something reasonable. The front z wheel has over a full turn of play
in it right now, mostly due to poor pinion to spindle rack
engagement. But thats another day too. One thing at a time, but I
can't stop trying to think ahead either.
I tried to heat the shop 3 years ago, with one of those horizontal,
blowered kerosene jet engine things. It worked fairly well at
heating the shop, but put so much moisture into the air that every
cold tool in it that didn't have a very fresh coat of WD-40 turned
bright red with rust, all in about 30 minutes. As its a wood shop
too, that was a lot of work cleaning up my wood planes, the
mini-lathe, this mill, lots of other hand tools. Needless to say
that heater left rapidly, with 3 of the first 4 gallons of fuel still
in the tank. So if I have anything out there that shouldn't freeze,
there is a 1500 watt electric on a thermostatic switch I can set for
about 35-40 degrees.
But I ramble and its late.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.29% setiathome rank, not too shabby for a WV hillbilly
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Copyright 2004 by Maurice Eugene Heskett, all rights reserved.