GE PACSystems RX7i, User Manual

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Chapter 6. Programming EGD Commands
102 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Q
(Word 7) EGD Command Number: Word 7 requests that a read EGD exchange operation occur. If the
command is processed successfully, it will result in data from a specified EGD exchange being read from the
client to the server.
(Word 8) Command Retry Time: Word 8 specifies the time (in milliseconds) the Ethernet Interface will wait
between retries when transferring the command. A total of four tries will be made to send the command. If no
response is received after the four tries (i.e. after four times the retry time value), an error status will be returned
in the COMMREQ status word. If the command retry is specified as zero, the default value of one second is used.
(Word 9) Local PLC – Memory Type: Words 9-11 specify the location in the local PLC where the Ethernet
Interface will get the data to be read from the remote EGD device. Valid values for Word 9 are listed in the
description of Read PLC Memory Command. The amount of data to be transferred is specified by the Exchange
Data Length (Word 18).
(Words 10 – 11) Local PLC – Memory Starting Address: Words 10 and 11 determine the starting address in
the local PLC where data is to be read from the remote EGD exchange. The value entered is the 32-bit offset (1-
based) from the beginning of PLC memory for the memory type and mode specified in Word 9. Word 10
contains the least significant 16 bits of the offset; word 11 contains the most significant 16 bits of the offset.
This offset will be either in bits, bytes, or words depending on the mode specified. (For example, if Word 9=16
and Words 10,11 = 2, 0 then the starting address will be %I9.) Valid ranges of values depend on the PLC’s
memory ranges. The user is responsible for assuring that this area is large enough to contain the requested
data without overwriting other application data.
(Word 12) Remote EGD exchange – Exchange Signature: Word 12 contains the 16-bit exchange signature
value to be compared at the remote EGD device. For remote PLCs, the exchange signature should be set to
zero if signatures are not being used. However, when signatures are enabled, the signature field can be set to a
non-zero value so that commands will be executed only if signatures match. In this case, mismatched
signatures will cause the command to return a failure status.
An EGD signature has the format
maj.min
, where
maj
is the major value and
min
is the minor value. The least
significant byte of this word indicates the minor value and the most significant byte indicates the major value.
For example, a value of 0xAABB refers to a
maj.min
value of 0xAA.0xBB.
EGD Signatures Enabled
(Y/N)
Signature Comparison
Desired
Recommended with
RMS of EGD
User Specified
Signature
No No No 0 (Default - no check)
Yes No No 0 (Default - no check)
Yes Yes Yes Current EGD signature
(Words 13 – 14) Remote EGD exchange – Producer ID: Words 13 and 14 contains the 32-bit Producer ID of
the desired exchange at the remote EGD device. Word 13 contains the least significant 16 bits of the Producer
ID; word 14 contains the most significant 16 bits.
(Words 15 – 16) Remote EGD exchange – Exchange ID: Words 15 and 16 contains the 32-bit Exchange ID of
the desired exchange at the remote EGD device. Word 15 contains the least significant 16 bits of the Exchange
ID; word 16 contains the most significant 16 bits.
(Word 17) Remote EGD exchange – Exchange Data Offset: Word 17 contains the 0-based byte offset of the
data to be read from the data portion of the exchange at the remote EGD device.
(Word 18) Remote EGD exchange – Exchange Data Length: Word 18 contains the length (in bytes) of the
exchange data to be read from the remote EGD device. The exchange data length may not exceed 1400 bytes
or the amount of memory available in the PLC for the selected memory type, whichever is less.
(Word 19) Remote Server – Network Address Type: Word 19 specifies the format of the remote PLC address.
Word 19 must contain the value 1. This indicates a dotted-decimal IP address expressed using a separate
register for each decimal digit.