From c415056194d6965d65c0fa18a38cdbc24660bb2c Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Tue, 15 Aug 2023 16:59:12 +0100
Subject: [PATCH 1/4] ! Feature: Change to a 5x5 display [breaking change]

---
 display.js                     |  8 ++++----
 machine.config.js              |  6 +++---
 readme.md                      | 10 +++++-----
 test-programs/fill-display.asm | 22 +++++++++++++---------
 4 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/display.js b/display.js
index 9fe6303..6a2c1b8 100644
--- a/display.js
+++ b/display.js
@@ -7,8 +7,8 @@ const { num2hex } = require('./logging.js');
  **/
 const printDisplay = (mem) => {
   const disp = mem[POINTER_TO_START_OF_DISPLAY_MEM];
-  for (let i = disp; i < disp + 16; i += 4) {
-    console.log(`${num2hex(mem[i])} ${num2hex(mem[i+1])} ${num2hex(mem[i+2])} ${num2hex(mem[i+3])}`);
+  for (let i = disp; i < disp + 25; i += 5) {
+    console.log(`${num2hex(mem[i])} ${num2hex(mem[i+1])} ${num2hex(mem[i+2])} ${num2hex(mem[i+3])} ${num2hex(mem[i+4])}`);
   }
 }
 
@@ -19,8 +19,8 @@ const printDisplay = (mem) => {
 const prettyPrintDisplay = (mem) => {
   const disp = mem[POINTER_TO_START_OF_DISPLAY_MEM];
   const num2pic = (n) => n > 0 ? '⚫' : '⚪';
-  for (let i = disp; i < disp + 16; i += 4) {
-    console.log(`${num2pic(mem[i])}${num2pic(mem[i+1])}${num2pic(mem[i+2])}${num2pic(mem[i+3])}`);
+  for (let i = disp; i < disp + 25; i += 5) {
+    console.log(`${num2pic(mem[i])}${num2pic(mem[i])}${num2pic(mem[i+1])}${num2pic(mem[i+2])}${num2pic(mem[i+4])}`);
   }
 }
 
diff --git a/machine.config.js b/machine.config.js
index b526793..63b8bc8 100644
--- a/machine.config.js
+++ b/machine.config.js
@@ -1,11 +1,11 @@
 module.exports = {
   "START_OF_DISPLAY_MEM": 0,
-  "POINTER_TO_START_OF_DISPLAY_MEM": 32,
-  "POINTER_TO_START_OF_KEYPAD_MEM": 33,
+  "POINTER_TO_START_OF_DISPLAY_MEM": 33,
+  "POINTER_TO_START_OF_KEYPAD_MEM": 34,
   "INITIAL_IP_ADDRESS":  48,
 
   // max number of times to step the CPU,
   // to stop endless loops
   // 0 = infinite
-  "CYCLE_LIMIT": 128,
+  "CYCLE_LIMIT": 256,
 }
\ No newline at end of file
diff --git a/readme.md b/readme.md
index 20c9b12..6bb9b1d 100644
--- a/readme.md
+++ b/readme.md
@@ -62,11 +62,11 @@ With verbose debugging output:
 
 ## Memory map / Peripherals
 
-- `00-0F` - display (4x4)
-- `10-1F` - keypad? (details TBD)
-- `20   ` - pointer to display memory
-- `21   ` - pointer to keypad memory
-- `22-2F` - reserved for future use / variable storage
+- `00-19` - display (5x5)
+- `20   ` - keypad (details TBD)
+- `21   ` - pointer to display memory
+- `22   ` - pointer to keypad memory
+- `23-2F` - reserved for future use / variable storage
 - `30   ` - initial value for IP
 - `30-FF` - free
 
diff --git a/test-programs/fill-display.asm b/test-programs/fill-display.asm
index aa09e53..1d7f36a 100644
--- a/test-programs/fill-display.asm
+++ b/test-programs/fill-display.asm
@@ -1,23 +1,27 @@
 ;; Fill display with $FF
+; updated for 5x5 display
+
+=pixelIndex $24
+=pixelFill $25
 
 LDA $00 ; Start of display
-STO $21 ; Pixel index
+STO =pixelIndex
 
-; store the $FF that we'll use to fill the screen
 LDA $FF
-STO $22
+STO =pixelFill
 
 @copy-to-display
-  LDA ($22) ; A = mem[$22] = $FF
-  STO ($21) ; mem[mem[$21]] = A = $FF
+  LDA ($25) ; A = mem[$25] = $FF
+  STO ($24) ; update pixel ... mem[mem[$24]] = A = $FF
 
 ; increment pixel index
-LDA ($21)
+LDA ($24)
 ADD $01
-STO $21
+STO =pixelIndex
 
-; if CF is set, then the display is full and we're done
-FHP 0
+LDA ($24) ; pixelIndex
+SUB $19   ; if pixelIndex - $19 == 0, we've reached the end
+FHP 2     ; Zero flag is #2
   JMP @copy-to-display
 
 END
\ No newline at end of file

From 1baa0ded328ce3027bfee815451372ef77bd515b Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Tue, 15 Aug 2023 17:01:51 +0100
Subject: [PATCH 2/4] Docs: Add an abandoned interval-timer-based refactor of
 the main CPU loop to dev notes

---
 notes/2023-08-15--dev-notes.md | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/notes/2023-08-15--dev-notes.md b/notes/2023-08-15--dev-notes.md
index ee9e88c..c74537a 100644
--- a/notes/2023-08-15--dev-notes.md
+++ b/notes/2023-08-15--dev-notes.md
@@ -34,4 +34,19 @@ Ken Shirriff, [The 6502 overflow flag explained mathematically](https://www.righ
 - `23-2F` - reserved for future use / variable storage
 - `30   ` - initial value for IP
 - `30-80` - free
-- `80-FF` - free, can be bank-switched
\ No newline at end of file
+- `80-FF` - free, can be bank-switched
+
+## Looping using an interval timer
+
+    const loop = setInterval(async () => {
+      step = step + 1;
+      // Temporary limit as a lazy way to halt infinite loops:
+      if (CYCLE_LIMIT && (step > CYCLE_LIMIT)) {
+        console.log('SIMULATION HALTING - reached cycle limit');
+        clearInterval(loop);
+      }
+      if (!CPU.running) clearInterval(loop);
+      if (CPU.IP >= CPU.memory.length) clearInterval(loop);
+      stepCPU();
+      await logCPUState(debug);
+    }, frameRate);
\ No newline at end of file

From 934f4c0f3f7a9d9b05b7fdfc6e60bd906517d18b Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Tue, 15 Aug 2023 17:02:02 +0100
Subject: [PATCH 3/4] Docs: Update to-do list

---
 notes/todo.md | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/notes/todo.md b/notes/todo.md
index 4d2a0e1..92fec6e 100644
--- a/notes/todo.md
+++ b/notes/todo.md
@@ -1,9 +1,5 @@
 # To do
 
-## Issues to fix
-
-- [ ] Allow tabs in assembler
-
 ## Research
 
 - [ ] Learn how the C64's PC gets initialized (what is the initial value? how is it set?)

From 2cceaa71f2e006c4a47b7d5fce603c9d1a029b74 Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Tue, 15 Aug 2023 20:53:51 +0100
Subject: [PATCH 4/4] Refactor: Rewrite fill-display: - make more use of
 constants - improve comments

---
 test-programs/fill-display.asm | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/test-programs/fill-display.asm b/test-programs/fill-display.asm
index 1d7f36a..a9b92a7 100644
--- a/test-programs/fill-display.asm
+++ b/test-programs/fill-display.asm
@@ -1,27 +1,25 @@
 ;; Fill display with $FF
 ; updated for 5x5 display
 
-=pixelIndex $24
-=pixelFill $25
+=*px  $24
+=fill $25
 
-LDA $00 ; Start of display
-STO =pixelIndex
+              ; Initialize variables...
+LDA $00       ; (Address for the first px on the display)
+STO =*px      ; Pointer to current px
+LDA $FF       ; ($FF is 'on', $00 is 'off')
+STO =fill     ; Stash value to fill with
 
-LDA $FF
-STO =pixelFill
+@paint
+ LDA (=fill)  ; (A = mem[fill] = $FF)
+ STO (=*px)   ; Paint pixel (mem[mem[*px]] = A = $FF)
 
-@copy-to-display
-  LDA ($25) ; A = mem[$25] = $FF
-  STO ($24) ; update pixel ... mem[mem[$24]] = A = $FF
-
-; increment pixel index
-LDA ($24)
+LDA (=*px)    ; Increment pixel pointer...
 ADD $01
-STO =pixelIndex
-
-LDA ($24) ; pixelIndex
-SUB $19   ; if pixelIndex - $19 == 0, we've reached the end
-FHP 2     ; Zero flag is #2
-  JMP @copy-to-display
+STO =*px
 
+LDA (=*px)    ; Test whether to loop or not...
+SUB $19       ; if *px - $19 == 0, we've reached the end
+FHP 2         ; (Zero flag is #2)
+  JMP @paint
 END
\ No newline at end of file