GE VersaPoint IC220PBI002, User Manual

Page: 135 / 202

GFK-1911B Chapter 8 Communications 8-15
8
Example 5, In the Event of an Error: Reading a Non-Existent Object on an
I/O Module with PCP Functions (Access to 5C00, Subindex 0 on a
VersaPoint RS-232 Communications Module, Slot 3)
This example write request has a similar structure to example 2. However, instead
of index 5FFF and subindex 2, index 5C00 and subindex 00 are requested.
As in example 2, the write response is used to indicate that the command has
been received. Processing on the I/O Station local bus starts afterwards. 81
hex
indicates the execution of the command, and 44
hex
indicates a basic error.
In this example, the PCP Read cannot be processed because the object does not
exist. The problem is indicated by the error code 06
hex
and 07
hex
within the object
data of the read response. The 2 bytes at the end may provide additional
information about an error, but they are not used in this case. The error is on the
lower-level local bus; it is not a DP/V1 error. 44
hex
as the response status always
indicates an I/O module error.
Write request (master -> slave)
Data Data Structure
5F 03 30 04 01 5C 00 00 Write/Slot/Index/Length/Read PCP/Index high/Index
low/Subindex
Write response (slave -> master)
Data Data Structure
5F 03 30 04 Write/Slot/Index/Length
Read request (master -> slave)
Data Data Structure
5E 03 30 28 Read/Slot/Index/Maximum length
Read response (slave -> master)
Data Data Structure
5E 03 30 06 81 44 06 07
00 00 Read/Slot/Index/Actual length/6 bytes of object data