OSWORD &FF

OSWORD &FF (255) Data transfer over Tube

Data transfer over Tube

This OSWORD call is installed by the Z80 Tube client.

 On entry:
   XY?0     =&0D (send block length)
   XY?1     =&01 (receive block length)
   XY!2     =I/O address
   XY!6     =Z80 address
   XY+10..11=data length, &0000=nothing to transfer
   XY?12    =command, 0=write to I/O, 1=read from I/O
   The control block is not updated on return.

The commands are the same as the Tube values:

• 0 - write single bytes to I/O
• 1 - read single bytes from I/O

The I/O address at XY!2 accesses the main I/O memory and whichever ROM happens to be paged in when the call is made - usually the current language. An updated version of the OSWORD &FF code uses the full I/O addressing range to access sideways ROMs and both banks of screen memory:

 &FFFFxxxx - Main memory
 &FFFExxxx - Currently displayed screen memory
 &FFFDxxxx - Shadow screen memory
 &FFxRxxxx - Sideways ROM/RAM R
 &FF8xxxxx - VDU workspace RAM

The OSWORD &FF code is available as a *runnable file that can be used with any second processor.

The code installed by the Z80 Tube client v1.36 and later also implements 2-byte data transfers, the data length must be even:

• 0 - write single bytes to I/O
• 1 - read single bytes from I/O
• 2 - write byte pairs to I/O
• 3 - read byte pairs from I/O

DOS fast screen control (80x86 DOS)

This OSWORD call is installed by the 80x86 DOS BIOS.

Commands are sent from the 80x86 via Tube Register 2 within the OSWORD protocol, so cannot be called through the normal OSWORD mechanism. The transaction must be done manually by the client by sending through Tube Register 2:

   &08 : Start OSWORD transaction
   &FF : OSWORD call &FF
   &00 : TxLen=0
 
 Then address/command pairs are sent. The address is sent, high byte then low byte.
 This address is updated for the data sent and wraps round from &7FFF to &4000. If
 the high byte is &00, no low byte is sent, and the routine finishes. Commands are:
   &FF : Read a single byte from through Tube register 1 to fill the following eight
         bytes of screen memory.
   &00 : Read eight bytes from Tube register 1 fill the following eight bytes of
         screen memory.
  Other: Loop back to wait for address or termination.
 
 Then finish with:
   &00 : RxLen=0, terminate the OSWORD call

See also

• OSWORD &05
• OSWORD &06
• OSWORD &72
• OSWORD &FA
• OSWORD &FB
• OSWORD &FC
• OSWORD &FD
• OSWORD &FE
• OSWORD &FE source code
• OSWORDs list at mdfs.net

References

Jgharston 14:30, 26 May 2009 (UTC) Jgharston 00:06, 31 January 2016 (UTC) Jgharston (talk) 11:05, 17 December 2024 (CET)