Yet Another Ben Eater Inspired Simple As Possible System
I'm following along with the excellent YouTube instructional series Building an 8-bit breadboard computer! by Ben Eater.
Note that he credits the book "Digital Computer Electronics" by Albert Paul Mauvino for many of the SAP (Simple As Possible) ideas.
I'm mostly keeping it the same as his computer except:
An enhancement to Ben Eater's 6502 address decoding logic based somewhat on @krischik STEEMIT article at https://steemit.com/hive-175254/@krischik/ben-eater-6502-kit-day-16.
This circuit adds a Dual 4 input AND chip (74LS21 per krischik) to recover unusable RAM in Ben's original design and a 3 to 8 decoder chip (74LS138) to provide additional device selects such as the additional VIA chip.
Ben Eater's amazing 6502 build series: https://eater.net/6502
Inspired by Ben Eater's 8-bit breadboard computer series on Youtube, but with an upgraded design that increases the RAM capacity from 16 bytes to 256 bytes and I also added a Micro Step Counter Reset (SCR) instruction signal to allow operations to finish earlier.