Horner APG XL4 OCS HE-ETN300 - Manual (Page 31)

SUP0740-07 CH.6
11/30/2009 Page 31 of 98 # 958
CHAPTER 6: ETHERNET GLOBAL DATA PROTOCOL (EGD)
6.1 EGD Overview
Ethernet Global Data (EGD) protocol is a GE Fanuc Automation protocol, which is designed for
simple, efficient data exchanges between peer devices on a network.
EGD protocol communicates using the UDP transport layer. Although this method of data transfer
is very efficient, it has no specific way to detect and recover lost data packets. However, since all
EGD data transfers are periodic, lost data packets will be repeated when their user-configured
time periods expire.
Caution: EGD protocol is not intended for one-shot event notification or for applications with
critical data, which can’t withstand being delayed as described above.
Each device on an EGD network can be configured as a Producer, as a Consumer, or both. A
Producer is a device that transmits Exchanges (blocks of data) to one or more Consumers. A
Consumer is a device that receives Exchanges from one or more Producers.
A Producer can transmit Exchanges directly to a specific Consumer, by sending them to the
Consumer’s IP Address (using Unicast IP Addressing). A Producer can also transmit Exchanges
to a Group of Consumers, by sending them to a Group ID (using Multicast IP Addressing). See
Section 2.3.2 (page 12) for more details regarding Unicast and Multicast IP Addressing.
An Ethernet Module supports up to 127 concurrent Exchanges, each of which can be either a
Producer or a Consumer of data.
6.2 EGD Terminology
Before configuring an Ethernet Module for EGD protocol, it is essential that the application
programmer understand the key EGD terms, which are shown in Table 6.1.
Table 6.1 – EGD Terminology
Term Definition
Exchange
A block of data sent by a Producer and received by one or more
Consumers
Exchange Number
A number (1 to 16,383), which along with the IP Address of the Producer,
is used to uniquely identify an Exchange on an EGD network
Producer An EGD network device configured to transmit one or more Exchanges
Consumer An EGD network device configured to receive one or more Exchanges
Produced Exchange
A block of data that a Producer sends to a Consumer or to a Group of
Consumers
Consumed Exchange
A block of data that a Consumer or Group of Consumers receives from a
Producer
Group
One or more Consumers that are configured to receive Exchanges,
which have been sent by a Producer to a specific Group ID
Group ID A number (1 to 32), which is used to identify a Group of Consumers
Production Period
A value (in milliseconds) that specifies how often a Produced Exchange
is transmitted to the network
Update Timeout
A value (in milliseconds) that specifies how long a Consumer will wait to
receive an Exchange, before considering it late. (Note: As rule of thumb,
a Consumed Exchange’s Update Timeout is normally set to at least twice
the corresponding Produced Exchange’s Production Period, plus 10
milliseconds.)