FILE---cherupakha.media.mit.edu:pub/6270/docs/DS1233-instructions.txt---

Several people have asked me for instructions to install the new reset
circuitry (needed for using the 'A1 processor) onto the older boards.

A few notes:

1.  The DS1233 chip is required when using current Motorola 6811
processors.  The older processors don't require this circuit (though
they will work fine with it).

2.  The most important difference between the revision 2.1x and 2.21
boards is that the 2.21 board includes the circuit presented here.
For more information on differences between these board revisions, see
the file pub/6270/rev2.21-assembly/v211-vs-221-differences.txt.

3.  The 'A0 processor will work fine in the latest board (rev 2.21),
but the 'A1 processor won't work in the older board (rev 2.1x), unless
the circuit presented here is installed.


       INSTALLING THE DALLAS DS1233 ONTO REV 2.1X 6.270 BOARDS

These instructions describe how to modify a Revision 2.1x 6.270 board
to accept the Dallas 1233 reset circuitry now present on the Revision
2.21 boards.  This modification allows the 6.270 board design to be
used with newer Motorola 'A1 suffix processors, which incorporate a
slightly different reset circuit that is incompatible with the older
6.270 board design.

Parts needed:  Dallas 1233 ``Econoreset'' chip, 0.01 uF capacitor,
1N914 signal diode, three 1K resistors.

Note:  prior instructions may refer to "1N4148" diodes.  These are
functionally equivalent to 1N914's in the 6.270 circuit and either
type (or both) may be used.


		      STEP-BY-STEP INSTRUCTIONS

The instructions assume the board is held such that the "top edge"
contains the labelling "6.270 Version 2.1x ROBOT CONTROLLER BOARD."

1.  Remove the following components:  C11 (4.7 uF), R9 (47K), C6 (2.2
uF), R8 (10K), R7 (47K), D4 (1N914), D5 (1N914), D6 (1N914), R5
(3.3K), RP3 (1K x 3).

2.  Install the new 0.01 uF capacitor in the position of R7.

3.  Install the DS1233 chip in the holes vacated by C6 and the upper
hole of R8.  Install so that the flat face of the DS1233 faces the
upper edge of the circuit board:

       ----------------------------------------------+
   "...ROBOT CONTROLLER BOARD"  	+-----+      |
	                                |o o o|  <-- | -- DS1233
					 \---/       |
                           vacant ---->  o o-o   <-- | -- 0.01 uF cap

4.  Install two 1K resistors in the place of the upper two resistors
of RP3 (i.e., to the left of LED11 and LED12).  

5.  Install the third 1K resistor in the remaining RP3 positions in
the following manner: insert (and solder) one lead of the resistor in
the bottom-most hole, and leave the remaining lead pointed upward
unconnected (for now).

6.  Install a 1N914 diode into the position of the C11 capacitor in
the following manner: insert (and solder) the anode (un-banded end)
into the left hole of the C11 position.  Leave cathode lead pointed
upward.

7.  Using thin wire (wire-wrap wire is ideal), jumper between the
cathode (banded end which is pointing up from the board) of the
``C11'' diode and the right-hand side of R12 (beneath the "CHOOSE"
button).  Clip the cathode short, just above the jumper.

Note:  steps 8 and 9 involve two jumpers that connect three points
together.  Do not clip leads until you have wired both segments of the
jumper. 

8.  Install a jumper from the lower hole of the R8 position (near the
DS1233 chip) to the un-connected end of the 1K resistor in the lowest
RP3 position.  

9.  Install a jumper from the un-connected end of the same 1K resistor
to the right-hand terminal of the main reset switch (SW2).  You will
need to run the jumper underneath the board; it is convenient to route
the jumper through a vacant hole such as either of the R9 holes.  The
right-hand terminal of the main reset switch is the one which -does
not- immediately connect to the large thick trace (system ground).
				   
		 ----END OF ASSEMBLY INSTRUCTIONS----


When the circuit is installed, the board should behave as follows.
When the board is powered on, the red "LOW BATT" LED should light for
about 1/3 second.  The LED will then turn off, and the board will
reset into run mode.  Note that previously, the board would power-on
into download mode.

To place the board in download mode, hold down the "CHOOSE" button and
press and release the reset button.  Continue holding the CHOOSE
button through the 1/3 second reset delay (during which time the LOW
BATT LED should be lit).  When the board comes out of reset, it will
be in download mode (evidenced by the SER XMIT LED being completely
off).

To reset the board normally, press and release the reset button.
After a 1/3 second delay, the board will reset.

When the alkaline cells which power the microprocessor circuit weaken,
you may notice a mode in which the board continually resets itself.
At this point the alkaline cells should be replaced.

	- Fred