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THE LATEST PROJECT UNDER CONSTRUCTION

Motorola MC6802 Mother Board with 16K8 EPROM, 32Kx8 Static RAM, 2 off MC6821 PIA's and a MC6850 ACIA

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There are two versions of this PCB design, the Version 1 has a RS232 clock speed covering 19.2K baud to 614.4 baud and Version 2 of the PCB covering 300 baud to 614.4 baud. The versions 1 board also has a "type with the other foot" design “feature” of the A0 and A1 transposed for both MC6821's. Please note the Memory Map adjacent shows the Version 1 memory map with the A0 and A1 in the transposed position. Reverse the registers in red for Version 2 boards.

 

To correct the programming of the Version 1 board with the A0, A1 transposed "feature" simply use the register addresses of both MC6821 EQU's as per the adjacent Memory Map. If the requirement is for for the RS232 baud rates to be  300 baud to 19.2K baud cut the trace between VCC pin 24 and both pins 22 and 23 of the MC14411 chip and then ground pins 22 and 23.

 

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