Publication 1734-UM009A-EN-P - June 2002
2-24 Configuring Your RS-232 ASCII Module
Transmit Handshake vs. Transmit Immediate Mode
This options defines when the 1734-232ASC module transmits data out
is serial port. Transmit Handshake mode is used primarily in Polled
I/O to prevent the 1734-232ASC module from repeatedly sending its
data buffer to the serial device each time an I/O command is received.
With Transmit Handshake active (default), the Master will change
the TX Transaction ID value in the message header whenever it wants
the 1734-232ASC module to send a serial string to the target serial
device. The module monitors the second byte (TX Transaction ID) of
the Poll command or explicit message to determine whether or not
the consumed data from the DeviceNet master is to be transmitted out
the serial port.
The module will not transmit the command data until it receives a
new TX ID value. Upon sensing a change in value of the TX ID byte,
the module transmits the data. It will initiate one serial transmission
for each change in the TX ID value, regardless of the data string value.
In Transmit Immediate mode, the 1734-232ASC module ignores the
TX ID byte value and initiates a new serial port transmission with each
message received from DeviceNet. This technique can be useful when
the target ASCII device is not affected by receiving the same data
multiple times and operates quickly enough so that message
overflows do not occur. This option may be most useful with explicit
messages.
These actions take place with either a Poll command or an explicit
message that writes to the consume assembly object or the serial port
object.
To Next Page
Loading...
