#133 Emulate the OEL/Volex TTX2000S

[Philip Kendall]

Add emulation of the OEL/Volex TTX2000S, a teletext/telesoftware adapter.

[Philip Kendall]

Patches (almost exclusively from Alistair Cree[1]) now in the feature-133-ttx2000s branch.

[1] who requested this feature in the first place ;-)

[Sergio Baldoví]

What it is needed to save/restore the status of this peripheral to a snapshot?

SZX block draft:

ZXSTTTX2000S

The state of the OEL/Volex TTX2000S teletext adaptor.

   // TTX2000S flags
   #define ZXSTTTX2000S_PAGED      1
   #define ZXSTTTX2000S_COMPRESSED 2
   #define ZXSTTTX2000S_CUSTOMROM  4

   // TTX2000S Block
   typedef struct _tagZXSTTTX2000S
   {
     ZXSTBLOCK blk;
     WORD wFlags;
     DWORD dwcbRam;
     DWORD dwcbRom;
     BYTE chChannel;
     BYTE chLine;
     BYTE chRam[1];
   } ZXSTTTX2000S, *LPZXSTTTX2000S;


Members

   blk
     The block header. The block id is ZXSTBID_TTX2000S ('T', 'T', 'X', '2').

   wFlags
     Various flags. This can be a combination of: 

       Flag                     Meaning
       ZXSTTTX2000S_PAGED       The TTX2000S's ROM and RAM are currently paged in.
       ZXSTTTX2000S_COMPRESSED  Specifies the RAM (and any custom ROM) have been compressed with the Zlib compression library.
       ZXSTTTX2000S_CUSTOMROM   A custom ROM is installed. The Zlib compressed or uncompressed ROM image begins after the RAM image at chRam. dwcbRom contains the size of the compressed (or uncompressed) data.

   dwcbRam
     Size in bytes of the Zlib compressed or uncompressed TTX2000S RAM. The uncompressed RAM size is always 1,024 bytes.

   dwcbRom
     Size in bytes of the Zlib compressed or uncompressed custom TTX2000S ROM (if one was installed). The uncompressed ROM size is always 8,192 bytes.

   chChannel
     Selected channel (0-3).

   chLine
     Current block line (0-15).

   chRam
     A Zlib compressed or uncompressed image of the TTX2000S's RAM. The uncompressed RAM size is always 1,024 bytes.

     If a custom ROM is installed. The image follows immediately after the RAM data.


Remarks

   None.

[Sergio Baldoví]

I'm curious about control port decoding. The interface responds to I/O address 0x7f and seems to be partially decoded by bit 7 (according to Fuse implementation).

That means that if you exit to BASIC and do "OUT 1,4" the TTX2000S memory gets paged in, right?

Also happens that with "OUT 0,4"?

[Sergio Baldoví]

And merged by [bce91f].