Handshake between PLC5/30 and SLC504

[Mark Buskell]

I got the two processors communicating over DH+.
In the PLC5 I have the following rung.

N52:0/0 ........... N50:96/0
---|\|-----------------( ) HandShake to SLC
XIO N52:2/0 OTE N50:96/0

N50:96/0 ........... T4:1, 10 SEC
---|\|-----------------TON Loss of Comm Timer
|
| N50:96/0 ............T4:2, 10 SEC
---| |-----------------TON Loss of Comm Timer

BST XIO N50:96/0 TON T4:1 1.0 10 0 NXB XIC N50:96/0 TON T4:2 1.0 10 0 BND

Either timer done bit sets an alarm.

In the SLC I have:

N52:0/0........... N50:96/0
---| |-----------------( ) HandShake to PLC

I am using message blocks and the heartbeat works great. N50:96/0 toggles on and off like it should. I have noticed that when I unplug the SLC and depending on the scan, N50:96/0 could be either on or off.

If I get comm loss between them, I need an alarm to tell me if the SLC goes down.

The only way I can figure it out so far is with two timers. Is there a simplier way to do this with 1 timer. I am also using RSView 7.0 and have an alarm tag set up to monitor comm loss.

 

[(8{)} ( .)]

It's easy to do with one timer.

You program an unconditional timer (TON) for the delay you want before alarm. Then you use one-shots on both the XIO and XIC in parallel to reset the timer using and RES command.

Something like this

N50:96/0 .......... T4:1
---|\|----[ONS]-+-----(RES)
|
N50:96/0 |
---| |----[ONS]-+


Good Luck,

(8{)} ( .)

 

[panic mode]

That's pretty common way to do it... What's the problem
with using two timers? It's only one timer and one rung more
than what you are looking for. Besides it's dead simple,
why change?
Using oneshots is an alternative, but I don't think
you can do it _exactly_ like emoticon suggested - at least not in SLC. I am pretty sure you would have to use two separate onshot rungs.

The way I look at it is you need to comment four bits instead of one timer and you get one more rung.

 

[Mark Buskell]

One Shot

The one shot works fine and allows me to use just one timer in the PLC5.

panic mode, you may be right about just using the 2 timers as being the most easily understood logic. I was looking for other examples
and maybe someone else had a better solution that I had not considered.

 

[(8{)} ( .)]

Well, if you'd like another way of doing this I usually transmit a register and use a DTR in the PLC-5 to detect a value change in the receiving PLC. The DTR resets the timer.

The problem with using 2 timers is that it gets expensive if you've got a lot of messages you want to test.

Regarding branched one shots, Mark asked about the code in the PLC-5, no problem with one shot branches there.


emoticon???

Good Luck,

(8{)} ( .)

 

[msinclair]

Mark - You could try using the ER bit of the Message Control Block. I don't know if you can customize the time out length though . . .