Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Manual de usuario descargar pdf (Pagina 151)

Data Encoding and Addressing

Chapter 6

6-14

PLC-4 Microtrol

PLC-4 Microtrol controllers use a form of logical addressing that specifies

the identification number of the controller in the loop, the section of

memory, and the bit address. To specify a PLC-4 logical address in a

command message, you would use an appropriate binary code. Note that

these binary codes let you address only PLC-4 words, not bits.

PLC-4 controllers can accept only PLC/PLC-2 type non-privileged

commands. The binary code for the PLC-4 logical address goes in the

2-byte field labeled ADDR in the PLC/PLC-2 message block formats

(Chapter 5). Put the low byte (Bits 0 through 7) of the binary address

code into the first byte of ADDR.

For example, suppose we want to address Storage Word 4 in Controller 3

in a PLC-4 Microtrol loop. The binary code for this address is:

00000000 00110100

In the command message that accesses this storage word, the ADDR field

would be:

00110100 00000000

First Byte Second Byte

ADDR

Physical Addressing

Physical addressing is the type of addressing a computer would use to

send a privileged command to a PC station. In particular, you would use

physical addressing to upload or download PC memory. The

recommended procedure for doing this is to use a series of physical read

or write commands that begin at Physical Address 0000 and proceed

sequentially to the end of PC memory.

Because of the differences in PC memory organization, the physical

addressing scheme varies somewhat with controller type.

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Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Manual de usuario Pagina 151