6-4
Section
Allocating PT Data to PT Memory
82
•
Allocate the PT status notify area to the DeviceNet Interface Unit’s input area if
at all possible. It won’t be possible to receive notifications from the PT if the PT
status notify area is allocated to the Unit’s output area. Also, exchanging data
by message communications takes some time, so changes in PT status may
not be recognized immediately if message communications are used.
•
When the DeviceNet Interface Unit is being used, the PT status notify area re-
quires one word more than it does with the regular Memory Link because the
first word of the PT status notify area is used to indicate the screen number of
the current PT screen. Refer to 1-5-2 Contrast with the Regular Memory Link
Method for more details.
PT Status Notify Area with the Regular Memory Link
Word
0
0
0
m + 1
15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0 Bit
Numeral/character string memory table number
(4-digit BCD or hexadecimal value)
PT status notify bits
m
PT Status Notify Area with the DeviceNet Interface Unit
Word
0
0
0
m + 2
15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0 Bit
Numeral/character string memory table number
(4-digit BCD or hexadecimal value)
PT status notify bits
m + 1
Screen number (4-digit BCD)
m
•
Some data is transmitted in both directions (PT
↔
Host) such as the window
control area, numeral memory tables, and character string memory tables.
When two-way data is allocated to the DeviceNet Interface Unit’s output area
or input area, only that one direction of data flow can be used. Only the control
from the host can be used if the data is allocated to the output area and only the
notification to the host can be used if the data is allocated to the input area.
Message communications provide two-way data exchange, but responses
may be delayed.
•
Do not allocate the following elements to the DeviceNet Interface Unit’s output
area. Doing so will disable the element’s functions.
•
Touch switch notification bits used for notification to the host
•
Numeral and character string memory tables used for numeral and char-
acter string inputs
•
Do not allocate the following elements to the DeviceNet Interface Unit’s input
area. Doing so will disable the element’s functions.
•
Lamp bits of lamps or touch switches
•
Numeral and character string memory tables written from the host
•
Bit memory tables
