Image Of The Leds; Serial Message Channel - Omron NT4S Operation Manual

Standard Mode

4.22.3 Image of the LEDs

4.22.4 Serial Message Channel

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Example: The cyclic poll area is set to DW 21 in the programming system:
Word Address DW
Word address +0 DW21 Write coordination byte
Word address +1 DW22 Message channel high-byte Message channel low-
Word address +2 DW23 Status LEDs 1 to 4
Word address +3 DW24 Status LEDs 9 to 12
Word address +4 DW25 Status LEDs 17 to 20
Word address +5 DW26 Status LEDs 25 to 28
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 .
0 0 0 0 0 0 0 0 0 0
Status LED OFF
1 1 1 1 1 0 0 0 0 0
Status
1 1 1 1 1 1 1 1 1 1
Status
Fig. 24: Truth table for status LEDs
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.
High Byte
LED ON
LED FLASHES
Section 4-22
Low Byte
Reserved
byte
Status LEDS 5 to 8
Status LEDS 13 to 16
Status LEDS 21 to 24
Status LEDS 29 to 32