ABB FENA-21 - Read and Write Blocks

PROFINET IO – Communication protocol 331
Read and write blocks
A read block is used in read requests and responses, while a write
block is used in write requests and responses. A request consists
of unique identifiers for the connection, addressing information and
the length of the record data. A response also contains two
additional fields for transferring information.
The table below shows the structure of the read and write blocks in
detail.
Field(s) Description Range Type
Service Request or Response
service
Request (0x00)
Response (0x80)
UI8
Operation Read or Write operation Write (0x08)
Read (0x09)
UI8
Block length Length of the block 0…0xFFFF UI16
ARUUID Identifier
•time low
•time mid
• time high and version
•clock
• node
UI32
UI16
UI16
Octet[2]
Octet[6]
API Application process
identifier
Device access
point (0x0000)
PROFIdrive
(0x3A00)
UI32
Slot Slot of the module
access point
(MAP/PAP)
0x01 UI16
Subslot Subslot of the module
access point
(MAP/PAP)
0x01 UI16
Padding 2 bytes
Index Index of the record data
object
0x2F
0xB02E
0xB02F
UI16
Data length Length of the data block 0…0xFFFFFFFF UI32