Micromod Micro-DCI: 53MC5000 PLC AND PRINTER INTERFACES - Manual (Page 35)

4.0 ALLEN-BRADLEY MODE
4.1 PURPOSE
The Allen-Bradley interface application permits data transfers between the Process Control Station
(PCS) and an addressed Allen-Bradley Programmable Logic Controller (PLC). Allen-Bradley DF-1
Protocol with Data Table and Allen-Bradley PLC-2 Data Table Addressing modes are supported.
4.2 DATA TABLE ADDRESSING
Data Table Addressing is the oldest Allen-Bradley addressing mode supported by the PCS Allen-
Bradley PLC Interface. Data Table Addressing was introduced by Allen-Bradley with the PLC-2,
which stored data in a common memory file called the Data Table. The PCS Allen-Bradley inter-
face reads and writes the data table as unsigned 16 bit integers.
Because of the large PLC-2 installed base, many support products (e.g., configuration tools, opera-
tor stations, etc.), which relied on the Data Table Addressing scheme, were offered by Allen-
Bradley and other third party vendors. Allen-Bradley, therefore, has traditionally provided some
form of Data Table Addressing in subsequent PLC family introductions, such as the PLC-5. For
this reason, the Allen-Bradley PLC-2 Data Table Addressing mode is supported by the PCS.
Data is written to and read from contiguous locations in the Allen-Bradley PLC Data Table. (A typi-
cal PLC memory data table is illustrated in Figure 3-3.) The boundary between the L and C data
types in the PLC should therefore be properly positioned.
4.3 INSTALLATION CONFIGURATIONS
As shown in Figures 4-1 through 4-3, typical Allen-Bradley installation configurations that are sup-
ported by the PCS are Point-to-Point, Data Highway, and DH-485 Network. It should be noted that
communication with network PLCs is bidirectional with one node; however, the read and write func-
tions can be separated across two PLCs if necessary. If more than one PLC must be accessed, a
suggested network application approach is to dedicate one PLC as the data source and destination
for the other PLCs on the network.
4.4 RS-232/485 ITB-PLC CABLES
A custom RS-232 cable is required for connection from the RS-232/485 ITB J1 to the PLC. The
recommended cable for this PLC application is illustrated in Figure 4-4. In the figure, one end of
the cable has a nine pin male plug that connects to J1 of the RS-232/485 ITB and the other end
has a 25 pin or 15 pin male or female plug as required by the PLC. The pin call-outs for the 15 pin
plug are shown in brackets in the figure.
The RS-485 TB2 lug connections for the RS-232/485 ITB are the standard five wire bundle:
T+ (out), T- (out), R+ (in), R- (in), and SH (shield).
Typical maximum cable lengths are 50 feet (15.2 m) for RS-232 and 4000 feet (1219 m) for RS-485.
Section 4. Allen-Bradley Mode
ALLEN
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