24 Feb
2013
24 Feb
'13
8:50 a.m.
On 02/24/2013 04:58 AM, Dave wrote:
On 24/02/2013 08:59, Nigel Williams wrote:
I don't see a crystal next to that chip. The sorta-nearby 24MHz
crystal is likely for the floppy controller...but unless that's divided
down to feed that possible-8048 chip, it may not be an 8048 because it
has no attached crystal. (it can also be fed from an external
oscillator, if memory serves...the 8051 definitely can)
Maybe reverse-engineer the oscillator wrapped around that 24MHz
crystal, then see where it goes. Compare that with the pinout of the
8048...if it goes to pins 2 or 3, that further suggests that Mr. 4430030
may be an 8048.
You (Nigel, not Dave) mentioned that you didn't think it was a
microcontroller because there's no ROM nearby. Don't put too much
weight on that, because the 8048 has an on-chip ROM.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
We've had some success decoding the various
LSI chips found within the
IBM Displaywriter System, in this case the external 8-inch floppy
drive subsystem (IBM 6360), but one last chip has stumped us, or more
accurately stumped our Estonian colleague who was familiar with the
IBM to Intel part number mapping, see here:
http://www.cpu-world.com/forum/viewtopic.php?p=164045#164045
Anyone with knowledge of how to implement the NEC D765D floppy disk
controller in a detached setup might be able to make a good guess as
to the function of the remaining 40-pin DIP IC (labelled 4430030) in
the picture?
http://i.imgur.com/VtMxSqj.jpg
is it another peripheral chip or perhaps a CPU? I'm guessing the
former since I don't see anything that might hold ROM code for a CPU.
Most of the date codes are towards the end of 1981 so 8144 is the latest
I can see. Thats around the time of the IBM PC announcement and I know
that used an Intel 8048 as a keyboard controller.
So an 8048 or similar, but if so why the 8225A as the 8048 would have
enough I/O lines for a floppy controller. 