2016-09-04
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Part 3 of building the RAM module for the 8-bit computer. In this video, we add the DIP switches and logic for manually inputting data in program mode. In run mode, data can be written from the bus into RAM.
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You can get all the components used in this video from any online electronic components distributor (Jameco, Digikey, Mouser, etc). See https://eater.net/bbcpu8-ram for more.
Complete parts list (everything in the RAM module):
- 2x 74LS189 (64-bit random access memory)
- 2x 74LS04 (Hex inverter)
- 1x 74LS173 (4-bit D-type register)
- 4x 74LS157 (Quad 2-to-1 line data selector)
- 1x 74LS245 (Octal bus transceiver)
- 1x 74LS00 (Quad NAND gate)
- 14x LEDs (9 red, 4 yellow, 1 green)
- 3x 1KΩ resistors
- 1x 0.01µF capacitor
- 22 gauge wire
- 5 volt power source (e.g., a USB phone charger)