more sane directory name, updated binaries

src/kernal/interrupts/nmi_lock.s

@@ -0,0 +1,60 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Routine to lock NMI interrupts, using a trick described here:
+// - https://codebase64.org/doku.php?id=base:nmi_lock
+//
+
+
+#if CONFIG_TAPE_HEAD_ALIGN
+
+
+// XXX consider broader usage of this method to make IO safer
+
+
+nmi_lock:
+
+	// We will have to change NMI vector to point empty routine,
+	// which will not acknowledge the interrupt - thus preventing
+	// the NMI to be triggered again
+	
+	// Our code considers zeropage address invalid, so put
+	// it there as a preparation
+
+	ldx #$00
+	stx NMINV+1
+
+	// We can now safelly replace the vector
+
+	lda #<return_from_interrupt_rti
+	sta NMINV+0
+	lda #>return_from_interrupt_rti
+	sta NMINV+1
+
+	// Stop timer A
+
+    stx CIA2_CRA // $DD0E
+
+    // Set timer A to 0, after starting NMI will occur immediately
+
+	stx CIA2_TIMALO // $DD04
+	stx CIA2_TIMAHI // $DD05
+        
+	// Set timer A as source for NMI
+
+    lda #$81
+    sta CIA2_ICR // $DD0D
+
+    // Start timer A to trigger the NMI
+
+    lda #$01
+    sta CIA2_CRA // $DD0E
+
+    // All done. Unmaskable interrupts are now masked.
+
+    rts
+
+
+#endif