cardiograph-computer/2023-09-05.md

Dev notes — 2023-09-05

Re: Blinkenlights

See 2023-08-31

That earlier note covers hexadecimal.

Here are some new notes on decimal display:

• https://en.wikipedia.org/wiki/Two-out-of-five_code -- used for representing the decimal digits using five bits.

• https://en.wikipedia.org/wiki/Bi-quinary_coded_decimal

  • The Remington Rand 409 and UNIVAC LARC encodings listed on that bi-quinary page are close to what I might want.

Here's my bi-quinary variation (similar to the IBM 650's):

5 q q q q

○ ○ ○ ○ ○    = 0
○ ○ ○ ○ ●    = 1 
○ ○ ○ ● ○    = 2
○ ○ ● ○ ○    = 3
○ ● ○ ○ ○    = 4
● ○ ○ ○ ○    = 5
● ○ ○ ○ ●    = 6
● ○ ○ ● ○    = 7
● ○ ● ○ ○    = 8
● ● ○ ○ ○    = 9

ISA

I think the group and addressing-mode sections need to be smaller, so that you can have more than 16 distinct operations?

Naming/design variations

• hex keypad version: “microcardiograph”
• toggle switches “minicardiograph”
• etc.

(allowing diff design for larger punch-card mainframe...)