Delta RMC151 - Manual (Page 435)

6 Communication
6.8.5. Communicating Directly over UDP
Master Ethernet controllers can communicate with the RMC using several methods. This topic
describes only one of those methods—using raw UDP packets—which is appropriate when the
master controller cannot use any of the other methods. Please review the other available
options in the Ethernet Overview topic before proceeding with this method.
This topic assumes that your controller has an established network platform and that you are
familiar with how to send and receive UDP packets on that platform. Some PLCs provide
access to UDP packets using function blocks, while embedded controllers may require using a
socket interface such as Berkeley sockets. Proper use of these interfaces is outside the scope
of this documentation.
Protocol Overview
The simplest UDP-based protocol supported by the RMC (firmware 3.31.0 or newer) is the
Delta Motion Control Protocol (DMCP). This topic describes how to form DMCP packets to
communicate with the RMC75E and RMC150E. The RMC75E and RMC150E listen for DMCP
requests on UDP port 1324. The client port number can be any number. This protocol is a
request/response protocol, meaning that for each request packet sent to the RMC, there
will be one response packet sent by the RMC.
For RMC firmware versions prior to 3.31.0, Delta recommended using the FINS/UDP
protocol for direct communication over UDP. For details, see the FINS/UDP topic.
Writing Data to the RMC
To send one or more registers to the RMC, send the following packet to the RMC:
Offset Data
(hex)
Description
0-1 nn nn Packet Length. Indicates the total length in bytes of
this packet, excluding this 2-byte field. This 16-bit
value is encoded with the least significant byte first.
2-3 00 02 Static Values. These bytes must always hold these
values.
4-5 nn nn Transaction ID. This value is simply echoed by the
RMC in its response packet. It can be used to match
responses with requests, since UDP does not prevent
packets from being delivered out-of-order or dropped.
6 15 Function Code. This byte must be 15 in a write
request.
7 nn Byte Order. Determines the byte order for all
following fields. Notice that the Packet Length byte
order is not affected by this field.
• Least-Significant Byte (LSB) First (00). For
example, the value 0x1122 will be encoded as 22
11.
• Most-Significant Byte (MSB) First (01). For
example, the value 0x1122 will be encoded as 11
22.
8-9 nn nn Starting Address (File). Gives the file number (f)
for the address (%MDf.e) to start the write at. The
order of the bytes in this 16-bit value is determined
by the Byte Order field.
10-11 nn nn Starting Address (Element). Gives the element
number (e) for the address (%MDf.e) to start the
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