Motorola MC6805P2


The MC6805P2 is one model of a family of microcontrollers from Motorola. It has 1100 bytes of user ROM and 64 bytes of RAM. One game that used it is Milton.


Milton game

Milton Bradley talking game.

Patent 4326710 has the schematic, although the circuit was changed to clock the MC6805 from the SP0250's 3.12MHz clock out, and the GROMs from that clock divided by 8 (390KHz).

Hardware description

full die shot Upper right pad is pin 4; pins are numbered CCW. There's an extra pad between 14 and 15.

die shot of MC6805R2 for comparison (it has more RAM and ROM, and A/D)

comparison of 6805 and 6804 dies

ROM array

ROM bits

raw ROM dump

ROM dump non-ROM areas are filled with NOP ($9D) to make disassembly easier

disassembly using unidasm zero-page ROM from $080-$0FF, user ROM from $3C0-$783, test ROM from $784-$7F7, vectors from $7F8-$7FF.


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.


Here's info about the similar MC68705P5


The game also has 2 TI TMC0430 GROMs.


6805 manual

SP0250 manual


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