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Collated tips from the web

Project Homepage: Building the 8 bit computer

A list of hints and tips that I've scanned from various posts around the web (warning: some may be in conflict with each other!).

Compiled by Chris B, Oct 2023 onwards

Boards​

  • Use pin header strips with (middle) pins removed to connect boards eg with power: [*5]

Power​

  • 100nF == 0.1uF (104 marking) ceramic capacitor per chip (or every few chips) across power rails [*1], or decoupling capacitors next to the chips [*2]
  • One 220uF electrolytic capacitor on each power rail [*1]
  • Big 1000uF capacitor where the power comes in from supply [*1]
  • Solder power cables to 3x2 header to make more secure [*1]
  • Note: LS chips need min 4.75v [*1]

Power rails:​

  • Connect all power rails
  • Central power rail
  • Side power rails

Resistors​

  • 1k [*2] (or 10k [*1]) resistors for pull up / down – DON’T LET INPUTS FLOAT
  • Pull all unused inputs up/down so that the output is high [3, pg2] (quote below)

    A good design rule is to tie unused inputs to a solid logic level. Inputs are usually tied to VCC through a 1 kΩ to 5 kΩ resistor

  • Some push buttons need resistor so they aren’t floating when disconnected (eg 1k on RAM write button) [*2]

LED​

  • Don’t rely on internal resistors, use current limiting resistors [*2]
  • 2.2k resistors for RED, 4.7k for Blue [*2]

Clock​

  • Monostable push button capacitor, raise to 0.33uF to let it have longer press
  • Addressing noise in the clock signal [*4]

Ram​

  • Double invert the clock line going into the Ram RC circuit to act as a buffer and prevent signal from the RC going back on the clock line.

References​

  1. /u/Lordmonoxide Tips https://www.reddit.com/r/beneater/comments/dskbug/what_i_have_learned_a_master_list_of_what_to_do/

  2. /u/CalliGuy Tips https://www.reddit.com/r/beneater/comments/ii113p/helpful_tips_and_recommendations_for_ben_eaters/

  3. AN-363CN.pdf: Guide to using TTL chips, from reddit tips: general/TTL%20AN-363CN.pdf

  4. Noise (?) issue in monostable mode of Ben Eater's Clock Kit module - with detailed description and working solution: u/dawidbuchwald (https://www.reddit.com/r/beneater/comments/edp1ls/noise_issue_in_monostable_mode_of_ben_eaters/)

  5. Adding 16 bits of mem: https://www.reddit.com/r/beneater/comments/mojfor/the_start_of_my_effort_to_add_16bit_memory/