Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 153)

Data Encoding and Addressing
Chapter 6
6-16
PLC-3 and PLC-5
PLC-3 and PLC-5 controllers use physical addresses that are related to
logical addresses by means of pointers. Since no two PLC-3/PLC-5
systems are configured identically, the pointers are not fixed. Therefore,
there is no algorithm for converting logical to physical PLC-3 or PLC-5
addresses.
The PLC-3/PLC-5 physical address is a word address. It goes in the
4-byte field labeled “PLC-3 physical ADDR” or “PLC-5 physical ADDR”
in the PLC-3/PLC-5 physical read or write command message format
(Chapter 5). The format for this physical address field is:
PLC-3/PLC-5 Physical Address
First Byte A24 A23 A22 A21 A20 A19 A18 A17
Second Byte 0 0 0 0 0 0 0 0
Third Byte A8 A7 A6 A5 A4 A3 A2 A1
Fourth Byte A16 A15 A14 A13 A12 A11 A10 A9
In this format, A1 through A24 represent the 1 to 24 bits of the physical
address value. For example, to address a command message to Physical
Word Address 12,200 decimal (002FA8 hex), you would use the
following binary code in the address field:
First Byte 0 0 0 0 0 0 0 0 (Value 00 Hex)
Second Byte 0 0 0 0 0 0 0 0 (Always 00 Hex)
Third Byte 1 0 1 0 1 0 0 0 (Value A8 Hex)
Fourth Byte 0 0 1 0 1 1 1 1 (Value 2F Hex)
The recommended procedure for uploading or downloading PLC-3 or
PLC-5 memory is to begin at Physical Address 0000 and proceed
sequentially to the end of memory. Since a single physical read or write
command can transfer only about 120 words of data, it will take many
such commands to upload or download the entire PLC-3 or PLC-5
memory. Therefore, each successive physical read or write should begin
at the next physical address after the one where the previous command
stopped.