Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 66)

6Ć26
When hardware handshaking is enabled for a port, the DTR
(Data Terminal Ready) pin on the Processor port is false when
more than 53 characters are in the receive buffer. The DTR pin
on the Processor port is true when the receive buffer is emptied.
Refer to the appropriate Processor manual for the port wiring
required for hardware handshaking.
Note: The DSR pin on the Processor port must be true when
hardware handshaking has been enabled. True is defined as +5
to +12 volts and false is defined as -5 to -12 volts.
The RTS (Transmit Status, Modem Enable) pin on the Processor
port can be controlled in an application task by using the
RTS_CONTROL@ function or by the operating system if
hardware handshaking has been enabled.
The purpose of the RTS signal is to bracket" the character
transmission. To bracket a character transmission, RTS must be
set true prior to the first character being transmitted and remain
true until all of the characters have been transmitted. The RTS
signal can be used to enable/disable any type of external
equipment, such as a triĆstate transmit modem, which requires
an enable signal to output characters.
When hardware handshaking has been enabled for a port, the
operating system will automatically bracket the character
transmission. RTS is set true when data is loaded into the
transmit buffer and remains true until all the characters have
been transmitted.
If the external equipment being controlled requires an
enable/disable time of more than 1 msec, RTS must be
controlled in an application task using the
RTS_CONTROL@function. Refer to the RTS_CONTROL@
function for a description of the operation and an example
program.
If hardware handshaking is enabled and RTS is set true using
RTS_CONTROL@, RTS will remain true after all the characters
have been transmitted so that the application task can use
RTS_CONTROL@ to set it false.