
13–10 PLC Addressing
Publication
17706.5.16 - October 1996
PLC5 Logical Addressing
PLC-5 processors, like PLC-3 processors, use a form of logical
addressing. With logical addressing, you specify the address for
each level (or sub-division) of PLC-5 memory, down to the smallest
subdivision you want to access:
With this processor You can specify up to
PLC5 4 levels of extended addressing, which is enough to address
any word in PLC5 memory.
PLC5/250 7 levels of extended addressing, which is enough to address
any word in PLC5/250 memory.
To send a command message to a PLC-5 node, you put the extended
address of the node in the field labelled PLC-5 SYSTEM ADDRESS
in the message block formats of your program. (See Chapter 7,
“Communication Commands.”) There are two types of PLC-5
logical addressing:
Logical Addressing
Type
Processors Description Page
logical binary
addressing
PLC5 A series of bytes used to encode up
to 4 levels of an address.
13-11
PLC5/250
A series of bytes used to encode up
to 7 levels of an address.
13-13
logical ASCII
addressing
PLC5 and
PLC5/250
Userspecified address in the same
form that you use at the programming
node.
This addressing lets any device
communicate with any other device,
without knowing the internal memory
structure of the target device.
13-15
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