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GW EIP/ASCII...
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Table 5-6 Serial port data transfer object instance attribute definitions
Attribute Description
Attribute 1: Transmit (PLC to
GW EIP/ASCII...) Message Data
This attribute transmits data out of a serial port on the GW EIP/ASCII.... In most
cases, incrementing the sequence number is optional. However, it is required if
the “Transmit Sequence Number Checking” option is enabled. The length must
be at least one and a maximum of 440 bytes. A “Get” command returns the last
successfully transmitted data message.
Attribute 2: Receive (GW EIP/ASCII...
to PLC) Message Data
This attribute provides the receive data while operating in the polling
communication method. The GW EIP/ASCII... increments the sequence number
for each new serial port packet received. A length of zero indicates no data was
received on the specified serial port. Two or more “Get” commands may return
the same data packet, but the messages will also have the same sequence
number. Serial packets up to 1518 bytes may be received while operating in the
“Write-To-Tag” field when set to Transfer to PLC . For serial packets over
440 bytes, the GW EIP/ASCII places the data into a sequence of tags. These
tags must meet the following criteria:
– Must be of type SINT.
– The entire sequence must be large enough to contain the maximum sized
receive packet plus four SINTs for the sequence number and length
parameters.
– All tags, except the last of the sequence, must be 444 SINTs in size.
– The tags must have the same base name and numbered in sequence. The
first tag is not be numbered, i.e., Com1_RxData, the second tag has a “2”
appended, i.e., Com1_RxData2, the third has a “3” appended, i.e.,
Com1_RxData3, etc.
– The sequence number and total length is placed in the first tag and the first
tag is the last tag updated. Therefore, once the sequence number is
updated, the entire serial packet has been received and the PLC can
process the data.
Attribute 3: Receive (GW EIP/ASCII...
to PLC) Produced Data Sequence
Number
This attribute gets and sets the “Produced Data Sequence” number. This is the
same “Produced Data Sequence” number sent to the PLC in all receive
communication methods.
Attribute 4: Transmit (PLC to
GW EIP/ASCII...) Produced Data
Sequence Number
This attribute gets and sets the “Transmit Produced Data Sequence” number.
This is the same “Produced Data Sequence” number sent to the
GW EIP/ASCII... in the Transmit Message data.