1 May
2013
1 May
'13
4:15 p.m.
At 04:17 PM 5/1/2013, Tony Duell wrote:
There's two ROMs on the board, and the only recognizable number on that
40-pin chip is that "8031". However, you may be right - week 31 of 1980
isn't unreasonable. And this is just the external interface card.
I've
opened up the drive. The external interface is to a "Data Path"
module that has a bunch of TTL and one large chip (40 -pin,
probably an
8031) with a Phillips logo. I think this is
confirmed to be an LMSI
rebrand.
I would not bet on it being an 8031, for several reasons.
The trivial one is that if it was from taht series, it would be more
likely to be an 8051 with an internal ROM. But amazingly, Philips used 6805-series micrcontrollers
in some CD-ROM
drives (and CD players). I have no idea why, but they did.
And the CD-ROM drive I mentioned has a 40 pin IC numbered PCF1801BP in
the data circuit. This is not a microcontroller, it's a mask-programmed
ULA which extracts the wanted data from the stram at the output of the
SAA7310 I suspect the chip in your drive is soemthing similar.
For the record, 3 of the RS422 drivers are drive by that IC. Pin 32 is
the clock output, it's inverted 3 times byy 4001 NOR gates (probably also
to delay it a bit). Pin 27 is the data output. nd pin 33 is Attention.
I've reassembled the drive as I'm about to build a cable. It's clear
that it's a simple pin-for-pin twisted pair for the first five pairs on
the DA15. Tracing the connector on the drive shows me drivers on pins
1/9, 3/11, 4/12, 5/13 and receiver on pins 2/10. Tracing the
controller shows a receiver on 1/9, 3/11, 4/12, 5/13 and a driver on
2/10. It would take a rather evil engineer to mix those pairs up.
-Rick