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13.3 Allen Bradley CSP
Ethernet-enabled Allen-Bradley legacy PLCs (such as the PLC5E and SLC-5/05
series) use a protocol called CSP (Client Server Protocol) to communicate over the
Ethernet network. The flavor of CSP used by these PLCs is also known as “PCCC”
(Programmable Controller Communication Commands) and “AB Ethernet”. The
interface card supports CSP for direct connectivity to these PLCs.
If a connection timeout or socket-level error occurs, the driver will trigger a timeout
event as described in section 10.7.5.
13.3.1 Tag Reference
Register contents are read from and written to the interface card via CSP by
reference to an integer “file/section number” and an “offset/element” within that file.
Reading is performed via the CSP “PLC5 Read” (DF1 protocol typed read) service,
and writing is performed via the CSP “PLC5 Write” (DF1 protocol typed write)
service.
The formula to calculate which register is targeted in the interface card is provided in
Equation 3.
(
)
offset10010- number fileregister target +×=
Equation 3
In Equation 3, “target register” ∈[1…1485], “file number” ∈[10…24] (which means
N10…N24), and “offset” is restricted only by the limitations of the programming
software (but is a value of 1485 max). Table 6 provides some examples of various
combinations of file/section numbers and offsets/elements which can be used to
access drive registers. Note that there are multiple different combinations of
file/section numbers and offsets/elements that will result in the same drive register
being accessed.
Table 6: CSP Target Register Examples
File/Section
Number
Offset/Element
Start Target
Register
N10 1 1
N12 99 299
N11 199 299
N20 7 1007
N24 85 1485
N10 1485 1485
In addition to providing access to the drive registers in their “standard” numerical
locations as mentioned above, the registers can also be accessed in a special
“assembly object” type format by targeting integer file N50. What this means is that
when N50 is targeted for reading, what is actually returned by the interface card is
the user-defined register data as ordered by the EtherNet/IP produced register