Omron KEEP (HR xx) instruction

Vicente Jasareno · Mar 14, 2004

Hello All,

Omron PLC KEEP instruction using an HR (holding Relay) memory address will hold information even when power to the PLC was off.

This is very useful for batch processing operation, for example, when no. of cycle and processing time is critical and can restart (of course not auto restart) the operation from where it stop due to power failure.

I am just sharing my experience.

Best regards,

Vic Jasareno

BobB · Mar 14, 2004

Data Memories (registers) also hold their value, unless you write "0s" into them.

Most PLCs have these functions available. For example, in Mitsubishi you set up the register memory retentive area you wish to use. The remainder of the register area is then not memory retentive. Very usefull.

beerchug

Eric Nelson · Mar 14, 2004

It's not necessary to use the set/reset KEEP(11) function to use the retentive (HR) bits. The HR area is retentive, period. It will 'remember' its state even if a simple latch is used.



|   WHATEVER                 HR0100

|-----] [------+------------( OUT )

|              |

|    HR0100    |

|-----] [------+

Correct me if I'm wrong, Bob. It's been a LOOOONG time since I've used an Omron...

beerchug

-Eric

BobB · Mar 14, 2004

Absolutely correct Eric.

beerchug

seppoalanen · Mar 14, 2004

There are SET and RSET instructions for that.

Jay Anthony · Mar 14, 2004

Thanks Vicente Jasareno for sharing that knowledege. We sometimes forget to post solutions rather than always questions.

Sleepy Wombat · Mar 14, 2004

You eventually might want to unlatch HR0100 though...

heh heh heh !



   WHATEVER      WHEN EVER    HR0100

----[ ]--------+---[/]--------( )

               |

   HR0100      |

----[ ]--------+

BobB · Mar 14, 2004

Look out!!! The Wombat woke up momentarily. No doubt gone back to

Pierre · Mar 14, 2004

BobB said:
Data Memories (registers) also hold their value, unless you write "0s" into them.

Sorry BobB but they also hold there value when its 0s.

BobB · Mar 14, 2004

Badly worded Pierre, should have read unless you write another value into them, such as "0s" into channels that contain numbers other than "0s". Old age catching up, that's my excuse.

Vicente Jasareno · Mar 14, 2004

Eric,

Correct me if I'm wrong, I think HR0100 below (assuming it's current state is 1) will reset to state 0 during first scan. This is one reason for using the KEEP instruction.

WHATEVER WHEN EVER HR0100
-------[ ]---------+--------[/]------------( )
|
HR0100 |
-------[ ]---------+

Best regards,

Vic Jasareno

Sleepy Wombat · Mar 14, 2004

The HR area retains its last known state ...therefore in the diagram HR100.00 will imediatley latch it self ON assuming that the WHENEVER is OFF upon power up.

If this config used a standard IO for example internal relay 200.00 in lieu of HR100.00, then indeed it would be reset upon power up.

Bobb.....

Old age catching up, that's my excuse.

It passed you a while ago ....

chavak · Mar 14, 2004

Vic,

As long as the n/o contact (when ever) do not have a transition HR0100 remains its state 1 in the first scan.

By the way, keep or set/reset instruction is to maintain the last state during a power disruption of the PLC.

BobB · Mar 14, 2004

A holding relay (HR) bit or channel will not reset itself on the first scan unless the ladder logic tells it to. You would have to use the first scan flag to reset it on the first scan.

If, however, the ladder logic tells it to reset, it will reset on the second scan.

Oh, lookout, Sleepy has woken up again, temporarily.

Omron KEEP (HR xx) instruction

Vicente Jasareno

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