Acyclic communication (DP/V1 and PCP)
7725_en_01
PHOENIX CONTACT
3-5
Note that when communicating with objects on local bus devices, the response should be
fetched using "Read". Otherwise the result will be overwritten during the next
communication. Communication is always carried out via DP/V1 index 47, and the object
index and assigned subindex of the I/O devices are transmitted as part of the data field.
Request and response
The section below provides additional information about the format of write and read access
(request and response).
The format for all types of access (request and response (positive), read and write) in DP/V1
is:
<DP/V1 header> <Data (PCP/DP/V1)>
The DP/V1 header for a positive DP/V1 response always has the following format:
<DP/V1 service (positive)> <Slot> <DP/V1 index> <DP/V1 length>
In the event of a faulty response, the format is as follows:
–
For a DP/V1 error:
<DP/V1 service (negative)> <Error decode> <Error code 1> <Error code 2>
–
For an I/O device error:
<DP/V1 service (positive)> <Slot> <DP/V1 index> <DP/V1 length>
<Error data (PCP/DP/V1)>
The <Data (PCP/DP/V1)> is optional depending on the service and has the following
structure:
The meaning of the individual parameters is as follows:
–
<DP/V1 service>:
In the request there is a distinction between DP/V1 read (5E
hex
) and DP/V1 write
(5F
hex
); in the error response there is a distinction between DE
hex
(read error) and
DF
hex
(write error).
Table 3-3
Structure of the data depending on the service
Access
Service
Data
Write objects
(IL PB BK DI8 DO4/EF-PAC)
DP/V1 write request
Object data
DP/V1 write response
None
Read objects
(IL PB BK DI8 DO4/EF-PAC)
DP/V1 read request
None
DP/V1 read response
Object data
Write objects
(I/O device)
DP/V1 write request
(PCP write)
Write PCP request/Invoke ID/Index high/Index
low/Subindex/Length of PCP data/x bytes of PCP object data
DP/V1 write response
None
DP/V1 read request
None
DP/V1 read response
Write PCP ack/Invoke ID/Status
Read objects
(I/O device)
DP/V1 write request (PCP
read)
Read PCP req/Invoke ID/Index high/Index low/
Subindex
DP/V1 write response
None
DP/V1 read request
None
DP/V1 read response
Read PCP ack/Invoke ID/Status/
Length of PCP data/x bytes of PCP object data
Содержание IL PB BK DI8 DO4/EF-PAC
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