2023-09-05 - Create note. Bi-quinary, plus quick notes on ISA and naming.

2023-09-05--dev-notes.md

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+# Dev notes — 2023-09-05
+
+## Re: Blinkenlights
+
+See [2023-08-31](2023-08-31--dev-notes.md#displaying-data-microprocessor-trainer-style)
+
+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...)