Janus Parameter Memory Map

Bridgeboard Parameter Register Map

all Bytes described here are described in the byteorder of the 8088.
Note: Words and longwords in these structures will be accessed from the Wordaccess space to preserve the Byteorder in a Word.
The 8088 will access Longwords by reversing the Words like a 68000 access to the word access memory.

Parameterbase:

  • A2088XT: F000
  • A2088T: F000
  • A2286: D000
  • A2386: D000
Function Description Datatype Size Parameter-
Addressoffset		 Amiga Address
      in Byte   Byte Word Grafic I/O
REF_RDY also used to handshake at 8088 reset UBYTE 1 0000 18000 38000 58000 78000
GO_286 unlocked to signal 8088 to initialize UBYTE 1 0001 18001 38001 58001 78001
JanusMemHead of ParamameterMem
Lock lock byte between processors UBYTE 1 0002 18002 38002 58002 78002
pad0   UBYTE 1 0003 18003 38003 58003 78003
68000Base rptr's are relative to this APTR 4 0004 18004 38004 58004 78004
8088Segment segment base for 8088 UWORD 2 0008 18008 38008 58008 78008
First offset to first free chunk RPTR 2 000A 1800A 3800A 5800A 7800A
Max max allowable index RPTR 2 000C 1800C 3800C 5800C 7800C
Free total number of free bytes -1 UWORD 2 000E 1800E 3800E 5800E 7800E
End of JanusMemHead of ParamameterMem
JanusMemHead of BufferMem
Lock lock byte between processors UBYTE 1 0010 18010 38010 58010 78010
pad0   UBYTE 1 0011 18001 38011 58011 78011
68000Base rptr's are relative to this APTR 4 0012 18012 38012 58012 78012
8088Segment segment base for 8088 UWORD 2 0016 18016 38016 58016 78016
First offset to first free chunk RPTR 2 0018 18001 38018 58018 78018
Max max allowable index RPTR 2 001A 1801A 3801A 5801A 7801A
Free total number of free bytes -1 UWORD 2 001C 1801C 3801C 5801C 7801C
End of JanusMemHead of BufferMem
Interrupts   RPTR 2 001E 1801E 3801E 5801E 7801E
Parameters   RPTR 2 0020 18020 38020 58022 78022
NumInterrupts   UWORD 2 0022 18022 38022 58022 78022
AmigaState communicate Amiga states to the PC
read by anyone, but written only by janus.library		 USHORT 1 0024 18024 38024 58024 78024
PCState communicate PC states to the Amiga
read by anyone, but written only by the PC		 USHORT 1 0025 18025 38025 58025 78025
JanusLibRevision   UWORD 2 0026 18026 38026 58026 78026
JanusLibVersion   UWORD 2 0028 18028 38028 58028 78028
JanusHandler
Revision		   UWORD 2 002A 1802A 3802A 5802A 7802A
JanusHandler
Version		   UWORD 2 002C 1802C 3802C 5802C 7802C
JanusHandler
HandlerLoaded		 zero before the PC is running,
is set to nonzero when the PC's JanusHandler is initialized		 UWORD 2 002E 1802E 3802E 5802E 7802E
PCFlag   UBYTE 2 0030 18030 38030 58030 78030
AmigaFlag   UBYTE 2 0032 18032 38032 58032 78032
Turn   UBYTE 2 0034 18034 38034 58034 78034
Pad   UBYTE 2 0036 18036 38036 58036 78036

Last Update: 05.06.2022