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6502 SBC: Breadboard Build

BB_A                                             BB_B                                           BB_C

   

 

Eagle: Schematic_01                  Eagle: Board_Layout_01

 

Initial schematic design was via Eagle CAD. The circuit was breadboarded circuit to test it.

 

Build and Testing Materials

After many years of reliable service, my personal choices for breadboard and jumper wire are:

- BB: https://www.radioshack.com/products/universal-solderless-breadboard

- Machine Pin Jumper Wires: https://www.circuittest.com/mb-940-flexible-wire-jumpers.html

 

Layout and Wiring

In the adjacent  thumbnail picture (click to expand) BB_A, the CPU, ROM and RAM DIP40 chips are laid out on the lower breadboard (BB).

Another breadboard is attached above the first BB.

Address bus lines from the CPU are attached to the upper BB via green wires.

Data bus lines are attached to the upper BB via blue wires.

In picture BB_B we have provided power to the CPU, ROM and RAM.

Address and data bus lines from the ROM are attached to the upper BB which is now serving as a bus for the system.

In picture BB_C, the RAM is wired in, too.

Power is from a 2-wire 5v source. The schematic/board layout show both the 2-wire and a 5v miniUSB connector. The top rail of the upper BB is split in half by Radio Shack. I used a low-forwarding-voltage diode (1N5817) to bridge the cap between halves and act as a polarity check.

 

Adjacent are the Eagle schematic and board layout for our circuit so far.

 

A simple variable (1Hz to 100Hz) CPU Clock for the system can be found here.

A more feature-rich version with single-stepping and which could include a 1MHz oscillator can be found here.

 

 

 

Updated 2022-09-24

 

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