S5 CPU928 TTY port

Hi all

I have a problem with a S135u CPU928. This CPU is connected to a pc which is running the program Wizcon, to control and do a follow up on the PLC. This pc crashed a couple of weeks ago, it is replaced now, and ever since I can't get connection to the PLC

The connection is made via the second port, a 25D female port. This sends a TTY signal to the pc, which is transormed by a convertor to a RS232 signal.

When is start the program I can see on the converter that the pc is sending to the PLC and the PCL is responding, but I get an error that there is no connection.

I have already installed another PC, a new converter and another cable, so the logical answer is that the communications port of the PLC isn't working properly.

The PLC is still working fine, so my question is can i test the port of the PLC if it's broken or not, and if not can I replace it? The PG port of the PLC is working fine.

Thanks in advance!

A good interface has steady 20 mA (or less, typical 16 mA) for both the loops.
Check the inlet current at pin 13 (CPU RX) and out current at pin 19 (CPU TX) with the cable connected.

"When is start the program I can see on the converter that the pc is sending to the PLC and the PCL is responding" If you can see the leds blinking (both) it seems the CPU interface works fine.

Your PLC is very old and I assume the broken PC was very old. The timing at the serial port of PC may be changed. May be a timing problem inside the serial chip or another problem.

Can you try the comunication with a very old PC and Wizcom?, Have you the same old operative system in the new PC?

I'll check the current at the pins, but I think that wil be fine because the converter recieves data from the PLC.

When the program starts it checks the PLC for data and the PLC responds, so the 2 LED's blink. But I'm not sure that the data the PLC is sending is correct! Could it be that the PLC can try to send data but the data is mixed up because the communications port is broken?

The "new" PC has the same hard- and software like the old one, we only swapped hard disks, all the rest is the same. I have tried many different baud rates and stop bits etc but nothing works:s

The version of Wizcon is old, its 7.5!

It is 13 years since i worked with a 928B with two onboard ports. So forgive me if I am wrong. Isnt it possible to use both ports for both PG and HMI functions ? Dont they more or less have the same functionality ?

The PG port of the PLC is working fine.

Click to expand...

If the above quote means that if you go online with STEP5 on the 1st port and it works OK, what happens then if you try to go online with the 2nd port ?
If on the other hand, the quote menas that you have put your Wizcon PC on the 1st port and it worked OK, then it looks like the PC is OK, but the 2nd port on the CPU is damaged.

-----
edit: Exactly which CPU type is it.
A 928 only has 1 port.
A 928B has a 2nd port where you can put a TTY module, but then both ports are 15-pin, not 25-pin.

I'm very new in this so I'm not sure if the two ports have the same functionality. I've been told that the second port is configured to communicate via TTY and is unable to communicate with Step 5.
The first port is working fine on Step 5, but I haven't tried it with Wizcon. If I try to go online with Step 5 on the second port via the converter I get the error message 'data overflow'... I haven't tried it directly on the port.

Hello Jeroen.

The PG uses TTY !
The 1st port on the 928B is definitely TTY, so when you connect your PG to that port, they are both using TTY with no adapter in between.

The 2nd slot on the 928B can be fitted with various modules, RS232, RS422, current loop (TTY or "PG").
It sounds like it has been fitted with a TTY module because of the TTY converter at the Wizcon PC. But it cannot have 25 pins, the PG/TTY port normally has 15 pins. Check up on this.
If it is indeed a PG/TTY module, try to connect your PG. You will then know if the PG/TTY module is OK.

Jesper, I think that port isn't a second PG port but is 25 TTY port and it was used for 3964(r) protocol.

The question is: how test a 3964(r) communication?

it is indeed a 25 tty port used for 3964 protocol.
Any idea how to test this anyone?

Dammit. Indeed there is one module called PG, and one called TTY. My bad.

About how to check 3964R:
You can download a demo version of an OPC server for 3964R. They are typically timelimited only, so they are perfect for troubleshooting like this. You can try to install it on another PC than the Wizcon PC, and use the available TTY converter.
You can then use an OPC test client to see if there is a connection to the PLC.
Try to google "OPC server 3964R" and there will be several good hits.