The PSDirect backend driver supports 4
different addressing types shown below:
|
Memory Type
|
Description
|
Address Range
|
Max Length
|
Example
|
|
DB
|
Data Block
|
DB0-DB65535,B0-B1000000
|
210
|
DB15,B0
|
|
M
|
Memory
|
0-1000 000
|
210
|
M0
|
|
I(E)
|
Input Image
|
0-1000 000
|
210
|
I0
|
|
Q(A)
|
Output Image
|
0-1000 000
|
210
|
Q0
|
The front end of the PSDirect driver follows the same data
addressing as the S7NT driver (Please refer to the S7NT driver
help).
Certain registers such as PE memory in the front end is mapped to
the “I” backend data type. Likewise PA registers are mapped to “Q”
in the backend.
For example, to use a PE register, you configure PE addresses in
CitectSCADA and “I” blocks in the backend, keeping in mind that a
PE register is a16 bit word so it requires 2 “I” bytes. No
configuration is required in the PLC.
Basically the address I, PE, E, PI all read from the backend “I”
blocks.
Keep in mind that the “I” poll blocks MUST map exactly to installed
physical analogue OR digital input cards. If there are gaps in the
address range, the PLC will not allow you to poll across them and
you will need to create many small blocks in the backend. However
this may cause lots of problems with the PSDIRECT front end because
it will attempt to block across these fragments and may fail. A
partial solution is to use the PSDIRECT6 32bit block protocol.
**Note if citect builds IO blocks across nonexistent addresses you
will get the "Nio*-Address Error nnnn" message in the backend, this
is non-critical but unavoidable.
|
