Omron NT15S, Operation Manual

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172
Standard Mode
Section 4-22
Example: The cyclic poll area is set to DW 21 in the programming system:
Word Address DW High Byte Low Byte
Word a0 DW21 Write coordination byte Reserved
Word a1 DW22 Message channel high-byte Message channel low-
byte
Word a2 DW23 Status LEDs 1 to 4 Status LEDS 5 to 8
Word a3 DW24 Status LEDs 9 to 12 Status LEDS 13 to 16
Word a4 DW25 Status LEDs 17 to 20 Status LEDS 21 to 24
Word a5 DW26 Status LEDs 25 to 28 Status LEDS 29 to 32
4.22.3 Image of the LEDs
The image of the LEDs enables the PLC to control the status LEDs in the function
keys. Functions that can be set for each status LED are the functions ON, OFF and
FLASHING. Whenever the controller sets a bit, the associated LED on the oper-
ating terminal is influenced accordingly.
It is important here that the size of the poll area and the polling time were set
appropriately. Not defining these additional parameters may cause problems when
the LED is addressed.
In the case of a function key that is to directly select a message mask, the status
LED is influenced by the message system. The message system uses this status
LED to indicate that a new message has been received but not yet acknowledged.
To be able to influence the status LED in this function key from the controller, the
message priority must be set to 0 (zero). See chapter 4.11.5
Status LEDs in the
Function Keys.
00000 00000
Status LED OFF
11111 00000
Status LED ON
11111 11111
Status LED FLASHES
Fig. 24: Truth table for status LEDs
4.22.4 Serial Message Channel
The serial message channel is a part of the cyclic poll area and is used to transfer
16-bit information. The numbers of serial messages, selection of message masks,
external selection of masks and transfer of control codes are made possible via this
data channel.
The following handshake is used for the information transfer: the PLC stores a
value (
.
0) in this data word. This value is then transferred to the operating termi-
nal which will write the value 0 into this data word again. This indicates to the PLC
that it can now transfer the next value. The value is interpreted by the operating
terminal and its function is executed.