Do (hopefully) MMU and serial setup

platforms/Neon816/Neon816.s

@@ -6,27 +6,65 @@
 .import   _Forth_ui
 .import   _system_interface
 
+; Bank Map from FB posting by Lenore:
+; 00 Bank Mapper (16 blocks of 4k each, configured via MMU)
+; 08-0F Bus Controller Peripherals
+; - 08 0000-003F MMU
+; -- 00: 0-3 Unused, 4-7: Upper RAM bits
+; -- 01: Bank
+; - 09 FDC
+; 10-1F Internal Bus Bridge
+; 20-27 Flash ROM
+; 28-3F Reserved for Flash
+; 30-3F Reserved for Expansion Flash
+; 40-47 Video RAM
+; 48-7F Reserved for VRAM
+; 80-87 RAM 1
+; 88-8F RAM 2
+; 90-FF Reserved for RAM
+
 .pushseg
 .segment  "FStartup"
 .proc     startup
           clc
           xce
           rep   #SHORT_A|SHORT_I
-          lda   #$0300            ; direct page for Forth
+          .a16
+          .i16
+          ; MMU setup, maybe.  Found at page $FF in Neon bank 0
+          ldx   #$001C
+          lda   #$8000
+:         sta   f:$080000,x
+          dex
+          dex
+          bpl   :-
+          ; NeonFORTH does this, presumably to initialize the serial port
+          sep   #SHORT_A          ; not necessary unless we were already native & long
+          .a8
+          lda   #$8D
+          sta   f:$10000A
+          lda   #$06
+          sta   f:$10000B
+          lda   #$00
+          sta   f:$10000C
+          rep   #SHORT_A|SHORT_I
+          .a16
+          .i16
+          lda   #$0000            ; direct page for Forth
           tcd
-          lda   #.hiword($020000)   ; top of dictionary memory
+          lda   #.hiword($0A0000)   ; top of dictionary memory
           pha
-          lda   #.loword($020000)
+          lda   #.loword($0A0000)
           pha
-          lda   #.hiword($010000)   ; bottom of dictionary
+          lda   #.hiword($090000)   ; bottom of dictionary
           pha
-          lda   #.loword($010000)
+          lda   #.loword($090000)
           pha
-          lda   #$0300            ; first usable stack cell (relative to direct page)
+          lda   #$0200            ; first usable stack cell (relative to direct page)
           pha
           lda   #$0100            ; last usable stack cell+1 (relative to direct page)
           pha
-          lda   #$09FF            ; return stack first usable byte
+          lda   #$03FF            ; return stack first usable byte
           pha
           lda   #.hiword(_system_interface)
           pha