Rockwell Automation 1203-SM1 SLC to SCANport Communication Module - Manual (Page 43)

4–15 Using Enhanced Mode
Publication 1203–5.9 –– October 1996
This field: Specifies:
Req Data
The actual data portion of the request message. Up to a maximum of
96 bytes of message data is available. This field is optional
depending on the type of message sent.
The response from the SCANport device appears in the message
buffer of the channel used (Channel 1 = M1:e.100–199, Channel 2 =
M1:e.200–299, Channel 3 = M1:e.300–399).
Figure 4.12 shows the structure of the message response buffers
inside the SLC M1 file.
Figure 4.12
M1 File Message Response Buffer Structures
Service (error or echo)
Class (echo)
Instance (echo)
Attribute (echo)
Response Length = n
Resp Data 2
Resp Data n
Resp Data 1
...
M0:e.b00
M0:e.b01
M0:e.b02
M0:e.b03
M0:e.b04
M0:e.b05
M0:e.bxx
e = slot location
b = buffer 0–7
Header
Information
Where:
This field: Contains:
Service
The same value as the service field of the request message if the
message transaction was successful. If an error occurred, the service
will be 0014H (20 decimal) and additional error information will be
placed in the response data field.
The error codes are provided at the end of this appendix.
Class
The same value that was used for the class field in the request
message.
Instance
The same value that was used for the instance field in the request
massage.
Attribute
The same value that was used for the attribute field in the request
message.
Response
Length
➀
The amount of data, in bytes, in this response. Most messages
contain 96 or fewer bytes of data. However, Get/Set Attribute
Scattered messages can be longer.
Resp
Data
➀
The actual data portion of this response. This field varies in length
depending on the message. If an error occurred, this field contains
the SCANport error code.
➀
The size of the returned packets determines the response length.
Some SCANport devices may return lengths greater than the actual
amount of data in the response. These products always return a
length which is a multiple of six. For example, a 1336 PLUS drive
may reply to a Read Number of Parameters message with a length of
six in the response. The first two bytes contain the complete
response data. The extra data bytes should be ignored.