Rockwell Automation 57C442 Data Highway Plus Interface Module - Manual (Page 29)

4-11
3, 4, and 5, only logical addresses represented as ASCII strings are
supported.
Command 3, Word Range Read, transfers a block of data from the
target registers at the remote address to the specified AutoMax
registers on the Data Highway Plus Interface module. Data can be
transferred to any file in the PLC-5 data image area except the B4 file.
The data is stored in the specified registers on the Data Highway Plus
Interface module. A maximum of one file (1000 registers) can be
transferred in a single request. The transfer cannot cross file
boundaries
Command 4, Word Range Write, transfers a block of data from the
specified AutoMax registers on the Data Highway Plus Interface
module to the target registers at the destination address. The data must
already exist in the registers on the Data Highway Plus Interface
module. Data can be transferred from any file in the PLC-5 data image
area. The data is stored in the specified registers on the Data Highway
Plus Interface module. A maximum of one file (1000 registers) can be
transferred in a single request. The transfer cannot cross file
boundaries.
Command 5, Read-Modify-Write, sets or resets specified bits in
specified registers in the data table at the remote address. The data
(AND and OR masks) must already exist in the registers on the Data
Highway Plus Interface module. A maximum of ten registers can be
modified in a single request. The transfer cannot cross file boundaries.
Note: The A-B controller at the remote address may change the states
of the original bits in memory before this command (command 5) can
write the word back to memory. Therefore, some bits may
unintentionally be overwritten. To help prevent this, we suggest that
you use this command to write into the storage area of a programmable
controller’s data table, and have the controller read the word only, not
control it.
In cases where any of the commands above generates multiple
messages on the network, for example, reading or writing more
registers than can fit in one Data Highway Plus message, the module
takes care of formatting and generating the messages required. The
GATEWAY_CMD_OK@ command is complete when a reply is
received for the last message.
4.2.5 Commands from Remote Stations
The Data Highway Plus Interface module will respond to the following
incoming commands from remote stations:
Command Function Description
OF 68 Typed Read / Read Block
OF 67 Typed Write / Write Block
OF 01 Word Range Read / Read Block
OF 00 Word Range Write / Write Block
OF 26 Read-Modify-Write / Write Bit
OF 02 Bit Write
Figure 4.6 – PLC-5 Command Set