Specifications

Appendix A - Smart-Frame Protocol Command Reference CARROLL TOUCH

A-28 Touch System Programmer’s Guide

Hardware_Flow_Control_On (41H) (A)

Command Description

When the host sends the Hardware_Flow_Control_On (41H)

command, the touch system uses hardware handshaking to regulate

serial communications with the host. Carroll Touch touch systems use

one of two hardware flow control methods, depending on the type of

touch system.

Modular RS-232 Controller

The Clear To Send (CTS) signal is used to regulate data transmission

from the host to the touch system. The touch system controls the state

of the CTS signal and asserts CTS by applying a positive voltage and

deasserts CTS by applying a negative voltage. If CTS is asserted, the

touch system is ready to receive commands. If CTS is deasserted, the

touch system is processing a command or performing some other

activity, and is not ready to receive commands.

The Data Terminal Ready (DTR) signal is used to regulate data

transmission from the touch system to the host. The host controls the

state of the DTR signal and should assert DTR by applying a positive

voltage and deassert DTR by applying a negative voltage. If the host

asserts DTR, the touch system transmits Smart-Frame Protocol reports

to the host. If the host deasserts DTR, no reports are transmitted from

the touch system to the host.

Smart-Frame Type Touch Systems

The hardware flow control method is the same as for the modular

RS-232 controller with one exception. If the Request To Send (RTS)

signal is deasserted, the Clear To Send (CTS) signal is always

deasserted, regardless of whether or not the touch system is ready to

receive commands. If RTS is asserted, the CTS signal reflects the ready

state of the touch system. If CTS is asserted, the touch system is ready

to receive commands; if not, the touch system is not ready.