OSWORD &7B

OSWORD &7B (123) - Modem comands Prestel Adaptor

The Prestel adapter modem can be in one of five states:
State 0 - on-hook, speaker off.
State 1 - off-hook, speaker on, modem off.
State 2 - off-hook, speaker off, modem off, dialing suitable.
State 3 - off-hook, speaker on, modem disabled, checking progress.
State 4 - off-hook, speaker off, modem enabled, data must be sent
at 75 baud and received at 1200 baud. The modem calls are used to
step through the five states and to monitor the dialling progress.
On entry:
 XY?0=command:
 0 - RESET to state 0.
 1 - STEP to next state. Do not use in state 4.
 2 - PULSE. Send a dial pulse. Use in state 2.
 3 - START-DIGIT. Initialise to send a digit, use in state 2.
 4 - END-DIGIT. Terminate dialling a digit, use in state 2.
 5 - DCD-CHECK. Exits with result in XY?0:
  0 - unpowered or no carrier
  1 - powered in state 0, carrier present in state 4.
To dial a number, STEP to state 2, for each digit, START-DIGIT,
PULSE for the number, END-DIGIT, STEP to state 4.

OSWORD &7B (123) - Modem commands COMMAND

On entry, XY+0=command as follows:
1 - Read status byte
On exit:
 XY?0: b0=offline/online, b1=XOFF sent, b2=XOFF received,
 b3=carrier present.

2 - Put byte to modem
On entry:
 XY?1=byte to send

3 - Get byte from mode
On exit:
 XY?0=byte
 XY?1=255 if valid, 0 if invalid

4 - Put string to modem
On entry:
 XY?1=length
 XY+2.. contains string

5 - Get string from modem
On exit:
 XY?0=length read
 XY+1.. contains string

6 - Read from remote computer
On entry:
 XY?1=maximum length
 XY+2..3=maximum time in centiseconds
On exit:
 XY?0=length of string
 XY+1.. contains string
If RETURN not receieved within the time, a Timout error
(103) is generated.

OSWORD &7B (123) - Move a block of memory HDFS

On entry:
 XY!0=source address
 XY!4=length
 XY!8=destination address
 Works across Tube and between Tube and I/O memory.

See Also

• http://mdfs.net/Docs/Comp/BBC/Oswords

Jgharston 13:17, 26 May 2009 (UTC)