prepare to add some code

src/asm/68k/amigatest/README.md

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+# Amiga verification export format
+
+"ROM" export format exclusively for verifying whether the Amiga emulation in Furnace is correct.
+
+do not assume this is the actual ROM export! it is nothing more than a register dump kind of thing...
+
+# process
+
+enable the setting in Furnace to unlock the export option by adding this to furnace.cfg:
+
+```
+iCannotWait=true
+```
+
+go to file > export Amiga validation data...
+
+put sample.bin and seq.bin in this directory.
+
+compile with vasm:
+
+```
+vasmm68k_mot -Fhunkexe -kick1hunks player.s
+```
+
+run a.out on Amiga. it should play the exported song.
+
+# sequence format
+
+## 00-0F: global
+
+- 00: do nothing
+- 01: next tick
+- 02 xx: wait
+- 03 xxxx: wait
+- 06 xxxx: write to DMACON
+- 0a xxxx: write to INTENA
+- 0e xxxx: write to ADKCON
+
+## 10-1F: per-channel (10, 20, 30, 40)
+
+- 10 xxxxxx yyyy zzzzzz wwww: set loc/len
+  - x: loc
+  - y: len
+  - z: loc after interrupt
+  - w: len after interrupt
+- 12 xxxx yy: initialize wavetable (xxxx: pos; yy: length)
+- 16 xxxx: set period
+- 18 xx: set volume
+- 1a xxxx: set data

src/asm/68k/amigatest/player.s

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+; Furnace validation player code
+; this is NOT the ROM export you're looking for!
+
+; incomplete!
+
+VPOSR = $dff004
+COLOR00 = $dff180
+
+cseg
+  move.l #0,d0
+
+main:
+  jsr waitVBlank
+  
+  move.w curColor,d0
+  move.w d0,COLOR00
+  addi.w #1,d0
+  move.w d0,curColor
+
+  jmp main
+
+waitVBlank:
+  move.l (VPOSR),d0
+  and.l #$1ff00,d0
+  cmp.l #$12c00,d0
+  bne waitVBlank
+  rts
+
+data_c
+
+curColor:
+  dc.w 0