tweak cx16 system init and reset to not reset Vera any more

uses new audio routine to silence the audio

codeGenCpu6502/src/prog8/codegen/cpu6502/assignment/AssignmentAsmGen.kt

@@ -435,7 +435,7 @@ internal class AssignmentAsmGen(private val program: PtProgram,
                         require(it.type == DataType.UBYTE)
                         val scopeName = (scope as PtNamedNode).scopedName
                         val comparison = PtRpn(DataType.UBYTE, assign.position)
-                        comparison.addRpnNode(PtIdentifier("$scopeName.$leftvar", it.type, value.position))
+                        comparison.addRpnNode(PtIdentifier("$scopeName.$leftvar", it.leftType, value.position))
                         comparison.addRpnNode(PtIdentifier("$scopeName.$rightvar", it.rightType, value.position))
                         comparison.addRpnNode(PtRpnOperator(it.operator, it.type, it.leftType, it.rightType, it.position))
                         comparison.parent = scope

compiler/res/prog8lib/cx16/syslib.p8

@@ -394,6 +394,11 @@ romsub $ff53 = joystick_scan()  clobbers(A, X, Y)
 romsub $ff56 = joystick_get(ubyte joynr @A) -> ubyte @A, ubyte @X, ubyte @Y
 romsub $ff56 = joystick_get2(ubyte joynr @A) clobbers(Y) -> uword @AX   ; alternative to above to not have the hassle to deal with multiple return values
 
+; Audio (bank 10)
+romsub $C09F = audio_init() -> ubyte @Pc                ; (re)initialize PSG and YM audio chips
+; TODO: add more of the audio routines here.
+
+
 asmsub kbdbuf_clear() {
     ; -- convenience helper routine to clear the keyboard buffer
     %asm {{
@@ -641,8 +646,9 @@ asmsub  init_system()  {
         lda  VERA_DC_VIDEO
         and  #%00000111 ; retain chroma + output mode
         sta  P8ZP_SCRATCH_REG
-        lda  #$80
-        sta  VERA_CTRL  ; reset vera
+        lda  #$0a
+        sta  $01        ; rom bank 10 (audio)
+        jsr  audio_init ; silence
         stz  $01        ; rom bank 0 (kernal)
         jsr  c64.IOINIT
         jsr  c64.RESTOR
@@ -650,7 +656,7 @@ asmsub  init_system()  {
         lda  VERA_DC_VIDEO
         and  #%11111000
         ora  P8ZP_SCRATCH_REG
-        sta  VERA_DC_VIDEO  ; keep old output mode
+        sta  VERA_DC_VIDEO  ; restore old output mode
         lda  #$90       ; black
         jsr  c64.CHROUT
         lda  #1
@@ -907,8 +913,6 @@ sys {
         %asm {{
             sei
             stz  $01                        ; bank the kernal in
-            lda  #$80
-            sta  cx16.VERA_CTRL             ; reset Vera (kernal doesn't do this?)
             jmp  (cx16.RESET_VEC)
         }}
     }

docs/source/index.rst

@@ -21,7 +21,7 @@ while still being low level enough to create high performance programs.
 You can compile programs for various machines with this CPU:
 
 * Commodore 64
-* Commander X16
+* Commander X16 (release R42 or newer is required)
 * Commodore 128 (limited support for now)
 * Atari 800 XL (limited support for now)
 

docs/source/targetsystem.rst

@@ -159,7 +159,7 @@ And for the Commander X16::
     cx16.restore_irq()     ; set everything back to the systems default irq handler
 
 
-The Commander X16 syslib provides two additional routines that should be used *in your IRQ handler routine* if it uses the Vera registers.
+The Commander X16 syslib does provides two additional routines that should be used *in your IRQ handler routine* if it uses the Vera registers.
 They take care of saving and restoring the Vera state of the interrupted main program, otherwise the IRQ handler's manipulation
 will corrupt any Vera operations that were going on in the main program. The routines are::
 
@@ -168,7 +168,11 @@ will corrupt any Vera operations that were going on in the main program. The rou
     cx16.pop_vera_context()
 
 .. caution::
-    It is advised to not use floating point calculations inside IRQ handler routines.
+    The Commander X16's 16 'virtual registers' R0-R15 are located in zeropage and *are not preserved* in the IRQ handler!
+    So you should make sure that the handler routine does NOT use these registers, or do some sort of saving/restoring yourself
+    of the ones that you do need in the IRQ handler.
+
+    It is also advised to not use floating point calculations inside IRQ handler routines.
     Beside them being very slow, there are intricate requirements such as having the
     correct ROM bank enabled to be able to successfully call them (and making sure the correct
     ROM bank is reset at the end of the handler), and the possibility

docs/source/todo.rst

@@ -12,12 +12,9 @@ RPN: Fix the TODO RPN routines to be optimized assembly in RpnExpressionAsmGen.k
 RPN: check BinExprSplitter disablement any effect for RPN?
 RPN: Implement RPN codegen for IR.
 
-- Move asmExtra vars into BSS as well, now are .byte 0 allocated
-
-
 For next minor release
 ^^^^^^^^^^^^^^^^^^^^^^
-- should X16 R0-R15 be saved in IRQ routine? At least document that you should not use them in IRQ handler?
+- Move asmExtra vars into BSS as well, now are .byte 0 allocated
 
 ...