Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 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:
0 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0
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.