Rockwell Automation 1760-xxxx Pico GFX-70 Controllers User Manual - Manual (Page 326)

Publication 1760-UM002B-EN-P - March 2005
6-20 Pico-Link and Point-to-Point Serial Connections
Example:
The read range of the active station is 1MD02.
The write range of the active station is 1MD03.
The read range of the remote station is therefore MD03.
The write range of the remote station is MD02.
Operating principle of the Serial Interface connection
The active station at the Serial Interface must be in RUN mode.
Data can only be exchanged with the active station in RUN mode.
The remote station must be in RUN or STOP mode.
The active station scans the remote station. The entire READ marker range is
transferred as a string. The entire WRITE marker range is transferred as a
string.
Sign of life detection Serial Interface, diagnostics contact ID09
To determine the proper functioning of the Serial Interface connection, the
diagnostics contact ID09 is provided on the active station of the Serial
Interface connection.
IMPORTANT
Data consistency
The data is located in the image range (data range
storing the marker states) of the active station
(1MD..) as well as in the image range of the remote
station (MD..)
Each station writes data to its own image range
asynchronously for data communication. As the serial
interface transfers large data volumes slower than the
devices overwrite the image ranges, the following
applies: one marker double word 1MD.., MD.. is
consistent.
Within a program cycle, a marker double word that is
overwritten via Serial Interface is not constant. The
data via the Serial Interface is written to the status
image over the course of the program cycle. This
means that a different marker value can be present at
the start of the program cycle to after the write
operation via Serial Interface.