6-11
since the command doesn’t specify which terminal it is meant for,
the base sends the following message back to the host:
*?CR
• If the Base Station receives more than 231 characters, it treats that
statement as an Illegal Command. If it sees more than 231
characters 5 times in a row, it transmits the following message to
the Terminal and shuts down:
Base Shut Down
Due to Host Logic
Error
You can re-initialize the terminal by sending *@EOT or by
powering the base off and back on.
Automatic Check Back
When a terminal checks back in to see if there is a change in instructions,
the host can send back the same prompt or send back a new prompt. The
check back occurs according to the time specified in the Terminal's setup,
(specified in increments of 5 seconds). When a check back occurs, the
Terminal clears the screen of the current prompt, and sends back the
following message:
Byte position Function Possible values
1 RF Terminal ID 0-9,A-Z,a-z,-=
2+ Check Back BEL (ASCII 07)
Last Termination of message CR (ASCII 13)
Base Station Initialized Message
Whenever the Base Station is powered up, it sends a message back to the
host as follows:
Byte position Function Possible values
1 BASE ID * (Base ID is fixed)
2+ Base Initialization DC3 (ASCII 19)
Last Termination of message CR (ASCII 13)
Since ASCII 19 is XOFF, the ASCII 19 character can be changed to ASCII
20 for XON/XOFF sensitive systems by changing the Base Station Setup.
See Chapter 2; RF System Setup for details.
The Base Station Initialized message is provided so that the host will
know that there has been a power interruption on the Base Station. When a
serial device powers up, the first byte transmitted is often garbage.
QBASIC handles the garbage character without incidence, but GWBASIC
does not unless ON ERROR GOTO is used to trap the error. Be aware of
this potential garbage-byte problem in your programming. To isolate and