from sean riddle:

"I was able to electronically dump the ROM using the non-user-mode pin. I used a 1 MHz
clock on the EXTAL pin with XTAL grounded, tied /RESET, /INT and TIMER high, and connected
NUM to +5. I tied the PORT A pins to +5 and ground using 8 1K resistors to set it to $9D,
the opcode for NOP, and I tied PORT C 3 high. The ROM contents were output on PORT B; I
captured the bytes using a logic analyzer."



Clocking off the incoming clock you get a pair of bytes per location twice. One of the
bytes is an incrementing count, so you throw away every other line twice, then convert it
to binary. The unused block from 500-77f was all ff's so it was easy to sync and they put
a text string in the user rom "LOGIMOUSE C7 3.2 (c) 1986 LOGITECH / R. Sommer Switzerland" 

MC146805F2P

RST/      01  28  +5
IRQ/      02  27  TIMER
NUM       03  26  PC0
EXCLK     04  25  PC1
          05  24  PC2
R2   PA0  06  23  PC3
R1   PA1  07  22  PB0
R0   PA2  08  21  PB1
          09  20  PB2
J4   PA4  10  19  PB3
J3   PA5  11  18  PB4
J2   PA6  12  17  PB5
J1   PA7  13  16  PB6
gnd       14  15  PB7  J0


J2 J1 J0
0  0  0  FIVE BYTE PACKED BINARY (MOUSE SYSTEMS CORT COMPATIBLE) INCREMENTAL STREAM
1  0  0  THREE BYTE PACKED BINARY PROMPT MODE
0  1  0  HEXADECIMAL PROMPT MODE *
1  1  0  RELATIVE BIT PAD ONE INCREMENTAL STREAM
0  0  1  RESERVED
1  0  1  MM SERIES INCREMENTAL STREAM
0  1  1  ABSOLUTE BIT PAD INCREMENTAL STREAM
1  1  1  MICROSOFT COMPATIBLE PROTOCOL INCREMENTAL STREAM

J4 J3
0  0     1200 BAUD
0  1     2400 BAUD
1  0     4800 BAUD *NOTE THE JUMPER SETTING 01010 SELECTS MM SERIES FORMAT AUTO BAUD RATE 
                    AND INCREMENTAL STREAM MODE, NOT HEXADECIMAL FORMAT 4800 BAUD
1  1     9600 BAUD