Horner APG XL4 OCS HE-ETN300 - Manual (Page 40)

CH.6 SUP0740-07
11/30/2009 Page 40 of 98 # 958
6.6 EGD Operation
Unlike other protocols, EGD protocol stops completely when the OCS (or RCS) is not in RUN
mode. In this case, EGD Produced Exchanges are not transmitted, and all received Consumed
Exchanges are ignored.
As soon as an OCS (or RCS), containing a configured Ethernet Module, is placed into RUN
mode, it will start exchanging EGD messages with other EGD devices on the network, as follows:
1. The Ethernet Module will transmit each configured Produced Exchange (see Section 6.4)
periodically, according to its Production Period (in milliseconds).
2. The Ethernet Module will expect to receive each configured Consumed Exchange (see
Section 6.5) at least as often as its Update Timeout (in milliseconds).
3. The Ethernet Module will maintain a Status Word for each Produced and Consumed
Exchange, as described in Section 6.7, and will report these Status Words in OCS (or
RCS) registers, if configured to do so (see Sections 6.4 and 6.5).
6.7 EGD Status Words
EGD Status Words allow an Ethernet Global Data user to obtain the operating status of each
EGD Exchange. The set of EGD Status Word values, implemented in the Ethernet Module, is a
subset of the ones used in GE Fanuc EGD devices. This is due to the fact that the Ethernet
Module does not support dynamically defined (at run time) EGD Exchanges.
Please note that both Produced and Consumed Exchange Status Words are written to local OCS
registers. This is the only case where a Produced Exchange can be configured to write to a local
register.
The Status Word for a Produced Exchange is updated each time the Exchange’s Production
Period expires. The Status Word for a Consumed Exchange is updated when new data arrives for
consumption or when the Exchange’s Update Timeout expires.
In normal operation, each EGD Exchange’s Status Word will always be 1 (OK), implying that new
data was successfully Produced or Consumed. If the application needs to be notified when a data
transfer has occurred on a given Exchange, the ladder program should clear the Exchange’s
Status Word register to 0 (IDLE) each time a non-zero event is detected.
6.7.1 EGD Produced Exchange Status Words
The Status Word for an EGD Produced Exchange can take on the following values:
0
IDLE - No new status event has occurred. The Ethernet Module initializes all Status
Words to 0, only at power-up and each time the OCS enters RUN mode. Subsequently,
the OCS application ladder program can write the value 0 to the Status Word, as an aid
in knowing when Ethernet Global Data production occurs (see Status Word 1).
1
OK - Data Produced. New EGD network data has been transmitted. A transition to 1
indicates production of data occurred since the last OCS ladder scan.
2
NO LINK - The Ethernet link was down when EGD data production was attempted. This
will occur, for example, if the Ethernet cable is unplugged from the OCS.