Allen-Bradley 1779-KFMR User Manual page 131

Only a computer can initiate privileged commands. The primary function
of these commands is to upload and download PLC-3 memory.
In "Application Fields," we showed the error-reply format. For PLC-3
messages, the error-reply message may have an additional field. If the
STS field value is F0, an EXT STS field is added following the TNS field.
PLC 3 Extended Error Reply Format:
In addition to the application fields found in the basic message set, PLC-3
message packets may also contain the following fields:
EXT STS — Contains extended status information in a reply
message. This field is included in the error reply only if the STS value
is F0 hex.
PACKET OFFSET — Contains the word offset between the DATA
field of the current message packet and the DATA field of the first
packet in the transaction. This offset value allows transactions that
require more than one command or reply message packet. The value of
Packet Offset is zero for the first packet in a transaction. This field is
only in command messages for which the transaction might take more
than one message packet to complete.
TOTAL TRANS — Contains the total number of data words to be
transferred by the current transaction. This field is only in command
messages for which the transaction might take more than one message
packet to complete.
Write Block
Use this command to write data into a block of words at the destination.
Use the address (L ADDR) field to specify a starting logical word
address; keep the address constant throughout a complete transaction. In
the first packet of a transaction, the packet-offset value is 00. In
subsequent packets of a transaction, use the packet-offset field to specify
the word offset (within the block) at which the write starts for the packet.
Use the total-transaction field to specify the number of bytes to read in the
total transaction. Use the SIZE field to specify the number of bytes to
read for the specific packet.
Chapter 8