cx16: added cx16.vaddr_autoincr() and cx16.vaddr_autodecr()

compiler/res/prog8lib/cx16/syslib.p8

@@ -539,6 +539,8 @@ asmsub vpeek(ubyte bank @A, uword address @XY) -> ubyte @A {
 
 asmsub vaddr(ubyte bank @A, uword address @R0, ubyte addrsel @R1, byte autoIncrOrDecrByOne @Y) clobbers(A) {
         ; -- setup the VERA's data address register 0 or 1
+        ;    with optional auto increment or decrement of 1.
+        ;    Note that the vaddr_autoincr() and vaddr_autodecr() routines allow to set all possible strides, not just 1.
         %asm {{
             and  #1
             pha
@@ -562,6 +564,84 @@ asmsub vaddr(ubyte bank @A, uword address @R0, ubyte addrsel @R1, byte autoIncrO
         }}
 }
 
+asmsub vaddr_autoincr(ubyte bank @A, uword address @R0, ubyte addrsel @R1, uword autoIncrAmount @R2) clobbers(A,Y) {
+        ; -- setup the VERA's data address register 0 or 1
+        ;    including setting up optional auto increment amount.
+        %asm {{
+            jsr  _setup
+            lda  cx16.r2H
+            ora  cx16.r2L
+            beq  +
+            jsr  _determine_incr_bits
++           ora  P8ZP_SCRATCH_REG
+            sta  cx16.VERA_ADDR_H
+            rts
+
+_setup      and  #1
+            sta  P8ZP_SCRATCH_REG
+            lda  cx16.r1
+            and  #1
+            sta  cx16.VERA_CTRL
+            lda  cx16.r0
+            sta  cx16.VERA_ADDR_L
+            lda  cx16.r0+1
+            sta  cx16.VERA_ADDR_M
+            rts
+
+_determine_incr_bits
+            lda  cx16.r2H
+            bne  _large
+            lda  cx16.r2L
+            ldy  #13
+-           cmp  _strides_lsb,y
+            beq  +
+            dey
+            bpl  -
++           tya
+            asl  a
+            asl  a
+            asl  a
+            asl  a
+            rts
+_large      ora  cx16.r2L
+            cmp  #1         ; 256
+            bne  +
+            lda  #9<<4
+            rts
++           cmp  #2         ; 512
+            bne  +
+            lda  #10<<4
+            rts
++           cmp  #65        ; 320
+            bne  +
+            lda  #14<<4
+            rts
++           cmp  #130       ; 640
+            bne  +
+            lda  #15<<4
+            rts
++           lda  #0
+            rts
+_strides_lsb    .byte   0,1,2,4,8,16,32,64,128,255,255,40,80,160,255,255
+        }}
+}
+
+asmsub vaddr_autodecr(ubyte bank @A, uword address @R0, ubyte addrsel @R1, uword autoDecrAmount @R2) clobbers(A,Y) {
+        ; -- setup the VERA's data address register 0 or 1
+        ;    including setting up optional auto decrement amount.
+        %asm {{
+            jsr  vaddr_autoincr._setup
+            lda  cx16.r2H
+            ora  cx16.r2L
+            beq  +
+            jsr  vaddr_autoincr._determine_incr_bits
+            ora  #%00001000         ; autodecrement
++           ora  P8ZP_SCRATCH_REG
+            sta  cx16.VERA_ADDR_H
+            rts
+        }}
+}
+
 asmsub vpoke(ubyte bank @A, uword address @R0, ubyte value @Y) clobbers(A) {
     ; -- write a single byte to VERA's video memory
     ;    note: inefficient when writing multiple sequential bytes!

docs/source/compiling.rst

@@ -301,6 +301,10 @@ Strange assembler error
 ^^^^^^^^^^^^^^^^^^^^^^^
 If the compilation of your program fails in the assembly step, please check that you have
 the required version of the 64tass assembler installed. See :ref:`requirements`.
+Also make sure that inside hand-written inlined assembly,
+you don't use symbols named just a single letter (especially 'a', 'x' and 'y').
+Sometimes these are interpreted as the CPU register of that name. To avoid such confusions,
+always use 2 or more letters for symbols in your assembly code.
 
 
 Community

examples/test.p8

@@ -1,26 +1,20 @@
-%import textio
-%zeropage basicsafe
 
 main
 {
     sub start()
     {
-        uword uw = 54321
+        cx16.set_screen_mode(128)
-        ubyte ub = 123
-        word sw = -12345
-        byte sb = -123
 
-        txt.print_uw(~ub as uword)  ;132
+        cx16.vaddr_autoincr(0,320*100+100,1,2)
-        txt.nl()
+        repeat 16 {
-        txt.print_ub(~uw as ubyte)  ;206
+            cx16.VERA_DATA1 = 0
-        txt.nl()
+        }
-        txt.print_uw(~sb as uword)  ;122
+        cx16.vaddr_autodecr(0,320*110+100,1,1)
-        txt.nl()
+        repeat 16 {
-        txt.print_ub(~sw as ubyte)  ;56
+            cx16.VERA_DATA1 = 0
-        txt.nl()
+        }
-        txt.print_w(-sb as word)    ;123
+
-        txt.nl()
+        repeat {
-        txt.print_b(-sw as byte)    ;57
+        }
-        txt.nl()
     }
 }