Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Manual de usuario descargar pdf (Pagina 154)

Data Encoding and Addressing

Chapter 6

6-17

PLC-4 Microtrol

PLC-4 Microtrol controllers use physical addresses that begin at 00 for

the first word of memory and continue to 5FF hex for the last word of

memory. Figure 6.11 is a map of PLC-4 physical memory.

Figure 6.1

PLC-4

Physical Memory

Physical Byte

Address

(Hex)

Read Only

Read/Write

Force

Table

I/O and Flags

Store Bits

Timers/Counters

Program

Area

Sequencer

Table

100

5FF

11703

Specifying a physical address in PLC-4 privileged commands requires

3 bytes. The first byte is the identification number for a particular

controller in the loop, and it is labeled “PLC-4 SEL” in the command

message formats (Chapter 5). The next two bytes contain the physical

address of a word in the selected controller’s memory, and they are

labeled ADDR in the command message formats (Chapter5). When

encoding the physical address, be sure to put the low byte of the address

value in the first byte of the ADDR field.

Symbolic Addressing

Symbolic addressing uses ASCII symbols to represent a logical address.

Only PLC-3 controllers can accept symbolic addresses. Before using a

symbolic address in a message, you must first define the symbol at the

PLC-3 or PLC-5 that is to receive the message (refer to

Publication 1775-801).

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Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Manual de usuario Pagina 154