6802 bally mpu

6802 bally mpu (-35 compatible...)

Bally -35 mpu	Bally 6802 mpu

Overviews of the 6802 mpu

reset circuit

schema 6802

pcb 6802

Here you see a 74ls00 and a 74hc4538. The 74hc538 is also battery buffered. -> This means, the reset line is high after power on until valid power (from the 2n3904 and the 2n4401) is detected.

pcb -35

Here you see the clock circuit (a 74s37 and a 9602). This circuit is replaced with a crystal and two caps.

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cpu

schema 6802

pcb 6802

Here you see a 6802 and the clock circuit: a 2.00 MHz. crystal and two caps.

pcb -35

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memory 5114

schema 6802

pcb 6802

Here you see a 5114 memory chip (a 1024x4-bit CMOS, 4 times larger than the 5101) and part of the reset circuit. (a 2n3904). The memory chip and the reset circuit are battery buffered.

pcb -35

Here we have our nice 5101 (256x4-bit CMOS) and the 6810 ram. The 6810 ram is not longer used, because this memory is part of the 6802.

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eprom 2764

schema 6802

pcb 6802

Here you can mount a 2764 eprom. This one could replace the two 2732 eproms for the game roms. (These ic-sockets are a nightmare by the way. They look nice and clean, but they are as worse as the ic-sockets on the -35 bally mpu).

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schema 6802

pcb 6802

The only difference between the 6802 and the -35 board is one resistor, but this is an important one:
The frequenz of this circuit is calculated in the following way: (formula took from here...)
forumula: 1,44/(((resistor between pin 7 and +5v) + 2 *(restistor between pin 6 and 7)) x (cap between pin 2 and gnd)).
Bally 35 board: 317 khz = 1.44 / ((36000 + 2 * 4700) * 0.0000001)
6802 board: 431 khz =1.44 / ((24000 + 2 * 4700) * 0.0000001)

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additional jumpers (for the 2764)

schema 6802

pcb 6802

These are additional jumpers. (The "old" ones are at the same places...) I think with these jumpers you can :
Replace the two 2732 eproms with one eprom
or
map the addtional 2764 eprom into a specfic memory location (This means a bally game with the double program size would be possible.....)

I got information from justin concerning a cybernaut with a 6802 MPU and a 2764 eprom:
Eproms
U7 - 2764
Jumpers - J2, J4, J7, J10, J11

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To summarize:
This 6802 mpu is a logical enhancment of the old bally-35 boards.
The differences:
6802 chip (instead a 6800)
no 6810 memory chip (is include in the 6802)
no clock circuit (has a crystal and two caps)
can work with one 2764 eprom
5114 memory chip (instead a 5101)
and a complete different reset circuit ( with a 74hc4538 and a 2n3904 for the 5114)
but :
It is full compatible to the bally-35 mpu..
It was prepared for the bally future:
Double progam size and quadruple ram size (dream of cool bally machines with this mpu...)
The game software is the same as for the bally-35 boards. So you can use the marvin3 guide...

any feedback welcome...

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