Communicating During Plc Scan: I/O Cycle; Accessing I/O Points; Figure 5-2 Plc Scan: I/O Cycle; Figure 5-3 I/O Word Configuration - Siemens SIMATIC TI505 386/ATM User Manual

5.2

Communicating during PLC Scan: I/O Cycle

Accessing I/O
Points
5-4 PLC Communications
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The naming conventions used for the I/O points in the module are from the
PLC perspective. For instance, 4 WX describes four analog words that will
be read into the PLC, while 4 WY are analog words that are an output from
the PLC. In other words, the points labeled as 4 WX are points that the
386/ATM writes to (remember, the PLC reads these points), and the 4 WY
points are read into the 386/ATM. See Figure 5-2.
Internal
diagnostics
I/O update
Relay
ladder
logic
Special
function
module
access
COMM
port
access
PLC CPU

Figure 5-2 PLC Scan: I/O Cycle

The IOREAD and IOWRITE commands allow you to gain access to the eight
local I/O points in the 386/ATM. The I/O points are configured locally in the
386/ATM as shown in Figure 5-3. You can configure the local I/O in your
PLC as a set of eight analog points.
WX1 WX2 WX3

Figure 5-3 I/O Word Configuration

PC COMM
4 WY
4 WX
Serial port
Serial
ports
WX4 WY5 WY6 WY7
Write to PLC
386/ATM Coprocessor User Manual
Application
Serial
1 or 2
386/ATM
I003101
WY8
Read from PLC
I003102