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 test for the problem, power up the Base without the serial cable connected. After you power the
Base up, plug in the serial cable. You will not see the “Base Initialized” message but it should not matter
when testing for the garbage data.
If a terminal is signed-on to the system, and the base station is re-initialized, the following message is sent
to the terminal:
Base Reinitialized X
Cycle Power on RF
Terminal and Sign-on
again to Restart_
where X is either a P (base initialization was power-related) or H (base initialization was host-related.
Control Keys for Possible Programming
There are some keys on the RF Terminal keypad that when pressed, can transmit special ASCII characters
back to the host program. This feature might be used by a programmer to allow the operator to review
transactions. You can use these keys for special program functions, such as scrolling thru data, backing
up steps, jumping, finishing a process, etc The keys are as follows:
Key Code transmitted to Host
UP ARROW key FS (ASCII 28)
DOWN ARROW key GS (ASCII 29)
LEFT ARROW key RS (ASCII 30)
RIGHT ARROW key US (ASCII 31)
BEGIN key ETB (ASCII 23)
END key CAN (ASCII 24)
SEARCH key VT (ASCII 11)