ghost RUN/STOP won't cause war restart together with RESTORE anymore

c64/,,config_generic.s

@@ -52,10 +52,10 @@
 // Keyboard settings
 
 // #define CONFIG_LEGACY_SCNKEY
-#define CONFIG_KEYBOARD_C128
+#define CONFIG_KEYBOARD_C128 // incomplete
 #define CONFIG_KEYBOARD_C128_CAPS_LOCK
 // #define CONFIG_KEY_REPEAT_DEFAULT
-#define CONFIG_KEY_REPEAT_ALWAYS
+// #define CONFIG_KEY_REPEAT_ALWAYS
 #define CONFIG_KEY_FAST_SCAN
 #define CONFIG_JOY1_CURSOR
 #define CONFIG_JOY2_CURSOR

c64/,,config_mega65.s

@@ -54,10 +54,10 @@
 // Keyboard settings
 
 // #define CONFIG_LEGACY_SCNKEY
-// #define CONFIG_KEYBOARD_C128
+// #define CONFIG_KEYBOARD_C128 // incomplete
 // #define CONFIG_KEYBOARD_C128_CAPS_LOCK
 // #define CONFIG_KEY_REPEAT_DEFAULT
-#define CONFIG_KEY_REPEAT_ALWAYS
+// #define CONFIG_KEY_REPEAT_ALWAYS
 #define CONFIG_KEY_FAST_SCAN
 #define CONFIG_JOY1_CURSOR
 #define CONFIG_JOY2_CURSOR

c64/,,config_testing.s

@@ -53,7 +53,7 @@
 // Keyboard settings
 
 #define CONFIG_LEGACY_SCNKEY
-// #define CONFIG_KEYBOARD_C128
+// #define CONFIG_KEYBOARD_C128 // incomplete
 // #define CONFIG_KEYBOARD_C128_CAPS_LOCK
 // #define CONFIG_KEY_REPEAT_DEFAULT
 // #define CONFIG_KEY_REPEAT_ALWAYS

c64/,,config_ultimate64.s

@@ -52,7 +52,7 @@
 // Keyboard settings
 
 // #define CONFIG_LEGACY_SCNKEY
-// #define CONFIG_KEYBOARD_C128
+// #define CONFIG_KEYBOARD_C128 // incomplete
 // #define CONFIG_KEYBOARD_C128_CAPS_LOCK
 // #define CONFIG_KEY_REPEAT_DEFAULT
 // #define CONFIG_KEY_REPEAT_ALWAYS

c64/kernal/interrupts/udtim.s

@@ -3,7 +3,7 @@
 // Official Kernal routine, described in:
 //
 // - [RG64] C64 Programmer's Reference Guide   - page 303
-// - [CM64] Compute's Mapping the Commodore 64 - page 232
+// - [CM64] Compute's Mapping the Commodore 64 - pages 27, 232
 //
 // CPU registers that has to be preserved (see [RG64]): .Y
 //
@@ -23,18 +23,33 @@ UDTIM:
 
 udtim_update_stkey: // entry to be used when interrupts are disabled
 
-	// Another action we have to perform is to copy the last row of keyboard to RAM,
+	// According to [CM64], page 27, another action we have to perform is to copy
-	// so that various routines can detect the STOP key press
+	// the last row of keyboard to RAM, so that various routines can detect the STOP
+	// key press. But something as simple as this would have created warm restart
+	// with M+N+SPACE+RESTORE due to ghosting - so the original ROM has to provide
+	// some protection here. I do not know what the mechanism there exactly does,
+	// but I hope the mechanism below will be compatible enough.
 
+	lda #$80
+	sta CIA1_PRA  // select all the rows except the last one
 #if CONFIG_KEYBOARD_C128
-	lda #$FF
+	ldx #$00
-	sta VIC_XSCAN // disconnect the extra C128 keys
+	stx VIC_XSCAN // connect all the extra C128 keys
 #endif
 
+	lda CIA1_PRB  // read the keys
+	eor #$FF
+	sta STKEY     // store reversed state - to filter out anything vulnerable to ghosting
+
+#if CONFIG_KEYBOARD_C128
+	dex           // puts $FF
+	stx VIC_XSCAN // disconnect the extra C128 keys
+#endif
 	lda #$7F
 	sta CIA1_PRA  // select the last row (bit to 0)
 
 	lda CIA1_PRB  // read the row
+	ora STKEY     // filter out what might be the reason of ghosting
 	sta STKEY
 
 	// Leave the CIA configured this way. It would be far better to disconnect

c64/kernal/keyboard/scnkey.s

@@ -37,10 +37,11 @@ SCNKEY:
 	lda #$00
 	sta SHFLAG
 
-	// Check for any activity
-
 #if !CONFIG_JOY2_CURSOR && CONFIG_KEY_FAST_SCAN
 
+	// Check for any activity - speed optimization, but cannot be done
+	// that early if we are to scan the joystick #2
+
 	ldx #$00
 	stx CIA1_PRA                       // connect all the rows
 #if CONFIG_KEYBOARD_C128
@@ -57,13 +58,10 @@ SCNKEY:
 #if CONFIG_KEYBOARD_C128_CAPS_LOCK
 
 	// First check if this is really a C128 - to avoid false positive
-	lda #$00
+	ldx #$00
-	sta VIC_XSCAN
+	stx VIC_XSCAN
-	lda #$FF
+	dex                                // puts $FF
-#if !CONFIG_KEYBOARD_C128
+	cpx VIC_XSCAN
-	tax                                // preserve the $FF, will be needed later
-#endif
-	cmp VIC_XSCAN
 	beq !+                             // branch if C64, C128 will keep some bits cleared
 
 	lda CPU_R6510
@@ -90,7 +88,7 @@ scnkey_bucky_loop:
 #endif
 	lda kb_matrix_bucky_testmask, y
 	and CIA1_PRB
-	bne !+                             // not pressed
+	bne !+                             // branch if not pressed
 	lda SHFLAG
 	ora kb_matrix_bucky_shflag, y
 	sta SHFLAG
@@ -165,7 +163,7 @@ scnkey_matrix_loop:
 	cmp #$FF
 	beq scnkey_matrix_loop_next        // skip if no key pressed from this row
 	cpy #$FF
-	bne scnkey_no_keys                 // clash, more than one key pressed
+	bne scnkey_no_keys                 // jam, more than one key pressed
 	// We have at least one key pressed in this row, we need to find which one exactly
 	ldy #$07
 scnkey_matrix_loop_inner:

c64/kernal/keyboard/scnkey_128.s

@@ -28,7 +28,7 @@ scnkey_matrix_128_loop:
 	cmp #$FF
 	beq scnkey_matrix_128_loop_next    // skip if no key pressed from this row
 	cpy #$FF
-	bne scnkey_128_no_keys             // clash, more than one key pressed
+	bne scnkey_128_no_keys             // jam, more than one key pressed
 	// We have at least one key pressed in this row, we need to find which one exactly
 	ldy #$07
 scnkey_matrix_128_loop_inner: