Rockwell Automation 1775-S5_SR5,D17756.5.5 User Manual PLC-3 FAMILY I/0 - Manual (Page 83)

Addressing DH and DH+ Data Transfers
Chapter 5
5-9
Logical ASCII data type addressing treats data being received and sent
from the floating-point data table section as a special case. The PLC-3
stores floating-point data using DEC-F format and the PLC-5 family store
the same data using IEEE format.
To handle this, whenever you send floating-point data using logical ASCII
data type addressing, the scanner translates the data into IEEE format
before transmitting on the link. Likewise, if floating-point data is received
using logical ASCII data type addressing, the scanner translates the data
from IEEE format into DEC-F format before storing into memory.
Word Range
A logical ASCII word range DH/DH+ packet does not indicate to the
receiving station anything about the data structure. The user assumes
responsibility for possibly sending unlike data types to the remote station.
For example, integer data to a BCD file.
The sending station simply sends the data from the data table address given
and the receiving station stores that same data at the indicated address. No
error checking is done for compatible data table areas.
To format a logical ASCII word range address, you enclose the address
parameters in single quotes (’):
Format: Example:
$’ address’,size $’N55:0’,15
Symbols are allowed inside the single quotes if they are defined in the
remote station.
Figure 5.7
Example of Logical ASCII Address that Accesses the 17th Word in File 4
$ ’
LogicalĆASCII word range delimiter
Word address in memory
LogicalĆASCII word range delimiter
Address delimiter
N4:17 ’