Installation manual

Publication 1747-RM001G-EN-P - November 2008
12-18 SLC Communication Instructions
• Data Table Address
This variable defines the starting address in the local controller. Valid
file types for the Data Table Address are shown below:
Only Bit (B) and Integer (N) file types are valid for Modbus Command
messages. Starting data table address for coil/input bit commands (1, 2,
5, and 15) require a bit address. Starting data table addresses for register
commands (3, 4, 6, and 16) require a word address.
Floating Point (F) file type is valid for Modbus Command messages for
Holding Registers (commands 03, 06 and 16) when data is configured
for 32 bits.
• Size in Elements
This variable defines the amount of data (in elements) to exchange with
the target device. The maximum amount of data that can be transferred
via an MSG instruction is 116 words for Modbus commands and is
determined by the destination data type.
The destination data type is defined by the type of message: read or
write. When a read message is used, the destination file is the data file in
the local or originating processor. When a write message is used, the
destination file is the data file in the target processor.
The mazimum number of elements that can be transmitted or received
are shown in the following table.
Table 12.8 Valid File Types for Data Table Address
Message Read Message Write
Bit (B) Bit (B)
Integer (N) Integer (N)
Floating Point (F) Floating Point (F)
TIP
Input, output, string, and RTC file types are not valid for
read messages.
TIP
The table is not intended to illustrate file compatibility. It
only illustrates the maximum number of elements that can
be exchanged in each case.