8 Aug
2000
8 Aug
'00
8:31 a.m.
It'll take a while for me to digest what you've said here. I looked at
the ][+ manual long enough to note that none of the bits used in the
interface go "straight through" which would have made life simple.
Consequently I'll probably build an I/O channel with power on the connector
and run it to something capable of latching/buffering bits in and out. That
will make the IIc capable of controller/monitoring nearly anything
electromechanical. Isn't there an 8-or-16-byte block anywhere in the IIc's
memory map that's not already used? This is what I've been trying to find,
among other things.
BTW, I caught the fact that the stepper phase signals are driven by a 9334,
which is a ttl addressable latch. I'm not even certain how it uses that
particular device, since it has several useful modes. The 16mA sink of the
9334 is quite significant as compared with most HCT-TTL workalikes will give
you, but it's not a relay driver. I was misled by the fact that someone
told me the ULN2803's were used to drive the stepper. I naturally assumed
that meant they were on the controller, since that's an 8-bit device and
there are only 4 phase drive signals to each drive. There's probably good
reason for that, however.
Dick
----- Original Message -----
From: Eric Smith <eric(a)brouhaha.com>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, August 08, 2000 1:38 PM
Subject: Re: Apple IIc (not IIC+) details
<snip lots of detailed info>
The 16 mA output from standard TTL is quite a bit as compared with the 6 ma
one gets from today's HCMOS, don't forget.
"Richard Erlacher"
<richard(a)idcomm.com> wrote:
> What? How does it generate FM? Is there a straightforward way to
create FM
> with the standard controller? FM is VERY easy to
deal with, while GCR
> requires one switch data rates, etc, all of which can be done, but it's
an
> unnecessary pain. How does it generate FM? is
that a function it does
> automatically or does it bit-bang it into a buffer and then ship it out
...
> or what??? I was NOT aware the Apple-][
controller could put out FM.
That
> would have made it able to read/write TRS-80
diskettes, wouldn't it?
Well .
. . maybe . .
.
It can do FM, but not IBM 3740 and equivalent formats. Woz's patent on
the controller in fact *only* describes FM; apparently he switched to
GCR later. In fact, the address fields on the disk are FM-encoded even
though the data sectors are GCR.
In the following discussion, not the careful distinction between channel The stepper
phase signals are of interest because they can sink some
current,
No, they can't. They're TTL signals. The drive has ULN2803A drivers.
> Now, is the rest of the memory map pretty much the same as on the ][+,
that
> is, can one rely on finding the small 256-byte
blocks associated with
each
"slot"? That's way more than I'd need for a channel.
No, the "slot" memory is taken up by the IIc ROM.