Rockwell Automation 1799-DASCII DeviceNet Serial Interface - Manual (Page 28)

28 DeviceNet Serial Interface Module
Publication 1799-IN012B-EN-P - July 2008
Concerning transmitting serial data to an ASCII device, the 1799-DASCII module
transmits character strings to the serial device that it has received from the
DeviceNet master via the following:
•
Poll I/O
•
Explicit Message
The character string is transmitted when either of the following conditions occurs in
the data within the DeviceNet message data field:
•
The specific number of bytes defined (Transmit Character Buffer Length) is received.
•
The defined End-of-String Terminator character is detected.
When either of these events occurs, the 1799-DASCII module stores the DeviceNet
string data into its internal buffer and transmits it out its serial port.
To transmit data to the serial device, the data must first be sent to the 1799-DASCII
module and then the 1799-DASCII module must send the data to the serial device.
The set-up for transmitting from the master to the 1799-DASCII module are
discussed first.
Consume Data Assembly Formats from DeviceNet Master
The assembly format options of the data to be sent from the DeviceNet master to
the 1799-DASCII module are shown below. The one selected depends on the
application. Refer to Transmit String Data Type Formats (parameter 22).
5 Nondelimited
string The current message has filled the buffer without a termination character, and is
being transmitted in total. This is not an error. It is caused by characters filling, but
not overflowing the receive buffer. This causes the 1799-DASCII module to transmit
the characters to the master.
6 Handshake
error This error occurs in Master-Slave Handshake mode. It indicates that the master has
requested a new data record from the 1799-DASCII module, but the 1799-DASCII
module has not indicated new data is available to be sent.
7 New data flag This bit is used only when the Master-Slave Handshake option is active. When the
1799-DASCII module receives a new data string into its serial port, it sets this flag in
its DeviceNet response message. The bit remains set for 1 produce message after
the master requests the new data. It resets.
Consume Data DeviceNet Format - Array Data Type
Byte 1 Byte 2 Byte 3 Byte 4 Byte 5-X (128 bytes max)
Rx ID Byte (Handshake
mode only) Transaction ID
Byte Reserved Reserved ASCII data (including optional
<terminator>.
Serial Status Byte
Bit Exception Description