Allen-Bradley 1779-KFMR User Manual page 144

70 — Read Immediate-Access Block
72 — Read Block
73 — Write Bit with Reply
74 — Write Bit with No Reply
75 — Write Block with Reply
76 — Write Block with No Reply
77 — Unprotected Write Byte Command
78 — Unprotected Read Modify Write Command
Each time-critical write is a protected command. That is, if its destination
is a PLC-2 programmable controller, it can only access an area of data
table memory designated by a memory access rung.
STS (Status) — When the command executor receives a time-critical
command, it replaces the CMD field with the STS field to generate the
reply. This one-byte field indicates a successful transaction completion
(00), a link-level error, or a time-critical error. Refer to Appendix A for
link-layer error codes. Time-critical error codes are as follows:
STS Code (Hex)
L ADDR (Logical Address) — This field specifies the logical starting
address of the block of memory affected at the destination station which
executes the command. If the destination is a PLC-2 station, this field
specifies a byte address. If the destination is a PLC-3 station, this
Chapter 9
Description