From 68ae53a24590a01d4a7996cc60c0f31b55e27116 Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Thu, 24 Aug 2023 12:17:24 +0100
Subject: [PATCH] (issues) issues - Add "execute JMP FF on startup" issue

---
 notes/issues/issues.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/notes/issues/issues.md b/notes/issues/issues.md
index c660488..59f7756 100644
--- a/notes/issues/issues.md
+++ b/notes/issues/issues.md
@@ -17,4 +17,30 @@ Full list of flags I want:
     -p --prettydisplay
     -mc --machinecode
 
+### #2 - Startup: Execute `JMP $FF`
+
+See [2023-08-24](../2023-08-24--dev-notes.md#cpu-start-up)
+
+... say that there's a 1-byte ROM at $FF.
+
+- `00-19` - display (5x5)
+- `1A   ` - pointer to display memory
+- `1B   ` - keypad: value of latest key pressed
+- `1C   ` - reserved for future use (bank switching flag)
+- `1D   ` - initial IP
+- `1D-FE` - free
+- `FF   ` - ROM (unwriteable) - pointer to initial IP
+
+- store `$1D` at `$FF`
+- make CPU execute `JMP $FF` on startup
+- make ROM unwriteable
+
+More step-by-step:
+
+  - Change memory from a Uint8Array to a regular array,
+    and make every entry { number | { type: 'ROM', value: number }}
+  - Store ROM as an object in machine.config.js
+  - Load ROM data into memory at CPU startup (`startCPU(RAM, ROM)`)
+
+
 ## Closed
\ No newline at end of file