GTCO Roll-Up II - Users Guide - Manual (Page 34)

Roll-Up II 34
buffer full; a modem to indicate carrier detect; and a time-shared computer that services
multiple users on a time-available basis.
There are two kinds of flow control:
■
Software flow control is often used over communication links where only a 3-wire cable
is used (Transmit Data, Receive Data, Ground) or over telephone lines. The Roll-Up II is
equipped for software flow control. It will immediately stop sending data when it receives
an ASCII XOFF character (CTRL-S, hex 13). Transmission will resume when it receives an
ASCII XON character (CTRL-Q, hex 11). Character flow control will work with the straight
through cable and the null modem cable.
■
Hardware flow control (also called modem lead flow control) uses one or more lines in
the RS-232C cable to send status signals from one device to another. The Roll-Up II is not
equipped for hardware flow control.
Remote Commands
NOTE: The following information is not required for normal Roll-Up II operation.
Roll-Up II can receive commands from other devices through its RS-232C port. Commands
cause the Roll-Up II to change the way it operates, to use certain coordinate formats and to
do other things directed by you or by an application program.
Commands offer another way to control Roll-Up II operation besides the Custom
Configuration Menu. Certain Roll-Up II functions can be carried out only through
commands.
If you are developing your own application software, be cautious about using commands in
your program. An interruption in power to the Roll-Up II or a Reset will cause it to discard
any command changes it has received. This could leave the program confused about what
the Roll-Up II is doing. A full system reset would then be needed to get the digitizer and
computer coordinated again.
Roll-Up II responds to three kinds of commands:
 GTCO Roll-Up II Standard Commands (with some omissions and additions)
 CalComp Emulation Commands
 Summagraphics Emulation Commands