Emsa HS500E manual T h e r n e t / I P H a n d s h a k i n g

C H A P T E R 5 : E T H E R N E T / I P P R O T O C O L

5 . 5 . 1 E t h e r n e t / I P H a n d s h a k i n g

To ensure that messages to and from the HS500E are properly delivered and received, a handshaking mechanism has been implemented that uses a pair of dedicated words in the exchange. The first two words in each Controller Tag are dedicated to handshaking.

When new information is generated, the producing device (data producer) increments a counter, and the consuming device (data consumer) copies that same counter value to another memory location to signal that the information has been processed.

5 . 5 . 2 E t h e r n e t / I P H a n d s h a k i n g E x a m p l e

In the example below, EMS_READ1 is the Read Tag for Node 1 and EMS_WRITE1 is the Write Tag for Node 1.

NOTE: [0] indicates the first word, [1] indicates the second word in a Controller Tag.

1The PLC writes a command to the Output area (of the Read Tag) and then increments the counter in EMS_READ1 [1].

2The counter in EMS_READ1 [1] is copied by the HS500E to EMS_WRITE1 [0] which acknowledges that it received the command.

H S 5 0 0 E – O P E R A T O R ’ S M A N U A L	P / N : 1 7 - 1 3 0 5 R E V 0 2 ( 1 2 - 0 5 )
	P A G E 4 8 O F 8 2