PCM Flash dump, Part 1


Step 1:  install jumpers
The 2 CPU signals *IPIPE/DSO and *IFETCH/DSI are not used during normal CPU operation.  During prototyping these 2 component pads would have 0 ohm resistors populated in order to connect these 2 signals to the 90 pin diagnostic connector.  For production they are not fitted.  Photo 1 shows the location of these jumpers on PCM service number 16207326.  The traces that connect them to the CPU are highlighted in blue, you should be able to follow the traces to the proper location on your PCM should it be different.  Figure 1 shows that these 2 pins are in fact *IPIPE/DSO and *IFETCH/DSI. Alternative:  The BDM wires for these 2 signals may be attached to the vias immediately above the jumpers, marked in yellow.  In this case the jumpers do not need to be installed.


Photo 1 -- Location of jumpers, vias, and traces for BDM signals *IPIPE/DSO and *IFETCH/DSI


Figure 1 -- Pinout of Southwest corner of 68332
 


Step 2:  Attach BDM connector
You will need a 5x2 piece of male header, and some wire-wrap wire to make the connector.  Use a different color for each signal if possible.  First attach the wires to the header strip per Motorola's recommended connection (see Figure 2).  Leave the wires plenty long to wrap around to the other PCB.  Figure 2 is the top view, and will be reversed when you are looking at the connector from the bottom soldering wires to it.

Figure 2 -- Recommended pinout for BDM connector

Once the wires are attached properly, attach the connector to the blue knock sensor module connector using a hot glue gun.  Use a nice large booger of hot glue, it'll make the soldered connections more reliable.  If this is done correctly it won't interfere with the fit of the knock sensor module.  See photo 2.  Remember to mark which end of the connector has pin 1.  I used a red marker on the end of the knock sensor module connector.


Photo 2 -- hot glue the BDM connector to the knock sensor module connector.


Step 3:  Attach the BDM wires
The signals needed for the BDM are all available on the 90 pin diagnostic connector, as shown in photo 3.  This connector pinout is common to 32 bit PCMs, so this step shouldn't vary by PCM service number.  The location and names of the signals are annotated on photo 3, and are also in table 1.  The rows are labelled X,Y,Z, starting at the top, and numbered 1-30 starting at the left.  Scrape off the conformal coating if present, cut the wires to length before attaching them, and when they're all done apply a dab of hot glue to each one.

Alternative:  The wires for *IFETCH/DSI and *IPIPE/DSO may be attached as described in Step 1, in which case they won't be attached as in Photo 3, and the jumpers from Step 1 won't be installed.
 
BDM connector pin diagnostic connector pin Signal BDM connector pin diagnostic connector pin Signal
1 X7 *DS 2 Y12 *BERR
3 X4 GND 4 Z29 *BKPT/DSCLK
5 X4 GND 6 Z30 FREEZE
7 Z12 *RESET 8 X11 *IFETCH/DSI
9 X25 VCC 10 X13 *IPIPE/DSO
Table 1 -- Connecting the BDM wires to the PCM diagnostic connector.
 


Photo 3 -- Connecting the BDM wires to the PCM diagnostic connector.


Step 4:  Check connections
Check continuity from the diagnostic connector in photo 3, to the BDM connector in photo 2.  Make sure that all the connections are good, no pins are shorted, and that the pins are in the proper place according to figure 1.  Figure 1 is the top view.

Step 5:  Power the PCM
This step is only if you'll be using the PCM on the bench.  You'll need a 12 volt power supply, capable of 1 amp output.  I tried a 14v/700mA wall wart and it wasn't up to the task.  Table 2 shows the power connections.  For PCM service number 16207326, connector C1 is the blue one and attaches to the digital PCB (the one with the 68332).  Connector C2 is the clear one that attaches to the analog PCB (with the knock sensor module connector).  You'll need a junkyard harness to power the PCM on the bench.  Cut the PCM connectors away from the rest of the harness.
 
PCM connector pin color function Connect to
C1-19 pink ignition feed +12
C1-20 orange battery feed +12
C1-21 black/white PCM ground GND
C1-56 black sensor ground GND
C1-60 black/white PCM ground GND
C2-21 black/white PCM ground GND
C2-60 black/white PCM ground GND

Once you're sure that all the connections are correct, power up the PCM.  Check to make sure that you have +5V across pins 9 and 3/5 of the BDM connector.  Once that checks out you're ready for part 2:  BDM hardware and software.  Reassemble the computer, and remove the knock sensor module cover in order to access the BDM connector (see photo 4).


Photo 4 -- Accessing the BDM connector when the computer is assembled.