Allen-Bradley 1779-KFMR User Manual page 197

Appendix B
Use this type of addressing when you send these commands to a PLC-2
station:
Protected Write Block
Protected Write Bit
Unprotected Read Block
Unprotected Write Block
Unprotected Write Bit
All Time-Critical Commands
All Remote Command Control Commands
When you send a time-critical or remote command control message to a
PLC-2 station, the address field (L ADDR) has a variable length of
two to four bytes. Byte 1 specifies the number of levels in the address
and should have a value of one because you can only address one level in
PLC-2 controllers. The remaining bytes contain the memory byte
address. If the byte address is 377 octal, Byte 2 must contain all ones and
act as a pointer to Bytes 3 and 4, which contain the actual byte address.
Here is an example addressing Logical Byte 416 (octal):
Byte 1
Byte 2 (if Address Is
Above 376 Octal)
Byte 3 (Low Byte)
Byte 4 (High Byte)
Here is an example addressing Logical Byte 236 (octal):
Byte 1
Byte 2
0 0 0 0 0 0 0 1
1 1 1 1 1 1 1 1
0 0 0 0 1 1 1 0
0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 1
1 0 0 1 1 1 1 0