Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 49)

Chapter 4
Configuring Your Decoder
4–22
Note: The Decode Trigger Mode (on second setup screen) must be set for
Host Command.
ENABLE HOST PORT BUFFER (bb) - Selecting YES will enable an 8K
buffer on the transmitter of the host port. This buffer allows the decoder to
decode and buffer messages to the host. You should use this feature in
applications where the host may be incapable of handling high burst rates of
data from the decoder. If NO is selected, the decoder will only buffer one
message.
RESPONSE MODE (cc) - The response mode specifies when the decoder
will send data to a host or activate an output module. In the triggered mode
of operation, you have two response options you can select:
1) End of Trigger - Selecting End of Trigger response will cause the decoder
to transmit data or activate discrete outputs after the end of a trigger. The
end of the trigger is determined by the triggering mode and may occur when:
•
Package detector no longer detects a package.
•
Trigger Off signal is received from the host.
•
Trigger is timed out by no-read timer.
2) After Valid Package - Selecting After Valid Package will cause the
decoder to transmit data or activate output modules immediately following a
valid package (fields per package count satisfied) or after a no-read is
detected.
If a valid package is never decoded, outputs and transmission of data occur at
the end of the trigger, as stated above.
HOST PROTOCOL (dd)- You can select one of ten options:
1) RS232: No flow control is selected.
2) RS232 XON/XOFF: XON/XOFF flow control is selected.
3) RS232 RTS/CTS-1: Modem controls (Request to Send-RTS, Clear to
Send-CTS, and Data Terminal Ready-DTR) are used. A description of these
control lines is provided in Chapter 6.
Note: The decoder has two modes of host communication which use the
modem control lines CTS, RTS, and DTR. RS-232 RTS/CTS-1 provides
flow control of communications from the decoder to the host. RS-232
RTS/CTS-2 provides bi-directional flow control. When communicating with
a 2760-RA or 2760-RB communications device that has modem controls
enabled, you must use RS232 RTS/CTS-2.
4) RS232 RTS/CTS-2: Modem controls (Request to Send-RTS, Clear to
Send-CTS, and Data Terminal Ready-DTR) are used. A description of these
control lines is provided in Chapter 6. Use RS-232 RTS/CTS-2 when you
connect the decoder to a 2760-RA or -RB that has modem controls enabled.