Newsgroups: comp.robotics
Subject: Re: Schematics for 6.270 board set
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tomd@risc.sps.mot.com (Tom Davidson) writes:

>Does anyone know if there are any schematics available for the COMPLETE
>6.270 board set?? Any printable format will do, Postscript is preferred.
>If they are in a schematic capture format, that would be OK, I could 
>probably get someone here at Motorola to print or translate them.

May I please refer people to the "6.270 Robot Builder's Guide," the
1992 version of the documentation which I wrote.  It contains complete
schematics to the version 2.11 board set.  This manual is available
via anon FTP to cherupakha.media.mit.edu in directory pub/6270.  It
-does not- have any of the PostScript printing bugs endemic to the
documentation on aeneas.mit.edu.

The schematic itself is split up over several pages, organized by
conceptual chunks of the circuit rather than arbitrary page breaks.
This was done because if I tried to put the entire schematic on one
8.5x11 inch page, the pin labels would probably print in 4 point high
numerals, rather unreadable.  So I compromised and split up the
schematic into multiple diagrams.  This may have been the wrong
choice, but I promise the whole schematic is there.


Many are wondering what the differences are between the rev 2.11
(1992) and rev 2.21 (1993) board sets.  They are nearly identical;
here are the differences:

1.  The rev 2.21 board uses a Dallas DS1233 reset controller chip to
provide battery backing of the static RAM.  This chip was deployed to
fix an incompatibility with newer versions of the 6811 processor.  It
replaces a hodge-podge collection of RC delays that was used in the
rev 2.11 and prior designs (i.e., it simplies the circuit rather than
complexifying it).

See file cher.media.mit.edu:pub/6270/docs/DS1233-instructions.txt for
an explanation of this circuit and the slight change it has on the
procedure to put the 6.270 board into bootstrap download mode.

2.  The rev 2.21 expansion board is laid out slightly better than the
rev 2.11:  the LCD connector no longer gets in the way of some of the
sensor input connectors.  The features and schematic of the expansion
board are unchanged.

3.  The rev 2.21 uses a 74hc273 chip for U5 in place of a 74hc374.  I
don't know why this substitution was made.  As far as I know, either
chip will work.

4.  The rev 2.21 uses a simplified infrared transmission circuit on
the main board, replacing an amplitude-controllable LM386 power op-amp
circuit with an on/off TIP120 darlington transistor.


I hope this information is helpful.  Let me know if there are any
problems retrieving or printing the files on the cherupakha machine.

	-Fred