will data transfer in parallel in GPIB interface?

[dragondriver]

Hi all,

  I have two devices (supporting GPIB) connected in serial and connect to the GPIB interface card. Those two devices have two different addresses and I use VISA module to send data in parallel. But the GPIB cables are connected in serial, so does it mean it will be locked when transferring data to one device? I think GPIB transfer rate is not that low (about 1Mbyte/sec) but it takes so long to transfer 500kB to the device (about 45sec).

[Dennis_Knutson]

The GPIB bus does not support parallel data transfers so you are certainly sending it that way.

You have not provided the instrument or your code so it.is impossible to say anything about your transfer rate but the 1MB is a theoretical maximum that you seldom achieve in the real world.

[dragondriver]

---

@Dennis_Knutson wrote:
The GPIB bus does not support parallel data transfers so you are certainly sending it that way.

You have not provided the instrument or your code so it.is impossible to say anything about your transfer rate but the 1MB is a theoretical maximum that you seldom achieve in the real world.

---

Here is the link for the device I have

http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=E3B19B3E9294659CE034080020E748...

The code is not written by me, but I extract the core part and show as below

You will see that there is only one GPIB interface (0), both device 1 and device 2 are connecting to the same card. The data sending to device 1 and device 2 is about 400kB (shown as xxxx.xxxxx. and yyyy.yyyyy).

[Dennis_Knutson]

That's meaningless. It is impossible to say what is in those strings and of course the reset is pretty time intensive and you have not provided any details on how you are calculating time. 45 seconds for the entire VI would seem reasonable.

[dragondriver]

---

@Dennis_Knutson wrote:
That's meaningless. It is impossible to say what is in those strings and of course the reset is pretty time intensive and you have not provided any details on how you are calculating time. 45 seconds for the entire VI would seem reasonable.

---

the first *RST almost spend no time. I can remove that command, it will be the same behavior. The data "xxxx....xxxxx"  and ""yyy....yyyy" are very long and big string (about 300kb - 500kb, I cannot show all of them here so I just shown the partial message. I start the code, it will run about 45 sec before the code done. I don't know why. Is it because two devices are connecting to the same GPIB card? Will it help if I buy one more GPIB card so each device connected to one GPIB card?

[dragondriver]

---

@Dennis_Knutson wrote:
That's meaningless. It is impossible to say what is in those strings and of course the reset is pretty time intensive and you have not provided any details on how you are calculating time. 45 seconds for the entire VI would seem reasonable.

---

By the way, why the conent of the string matter? It is just the data sent to the device and fill into the built in memory.

[Dennis_Knutson]

That question makes no sense. It would of course matter the strings were 10 bytes or 100 kb. From an image, it was impossible to say.

You need to check the specs and talk to Agilent. There is no issue with LabVIEW.

And yes, you can write to 2 different instruments at the same time with 2 controllers.

[dragondriver]

---

@Dennis_Knutson wrote:
That question makes no sense. It would of course matter the strings were 10 bytes or 100 kb. From an image, it was impossible to say.

You need to check the specs and talk to Agilent. There is no issue with LabVIEW.

And yes, you can write to 2 different instruments at the same time with 2 controllers.

---

Anyway, not offense, I am not talking about the size of the strings, I keep having my question about the topic "will data transfer in parallel in GPIB interface?", your said post is no but you said you want the model or code, so I post the code. Well, anyway your second reply always answer my question, so I just want to post the code to confirm that. To me, sending 10k or 10byte will affect the transferr time in the code but it makes no difference to the answer of the topic because what I want to know is if I have only one GPIB interface card and have two device connecting to the same card, even I have the address of each deivce different, will the data transfers to device 1 not parallel to data transfers to device 2, i.e. one device will wait the other device's transfer finish so to start it's own transfer?

[Dennis_Knutson]

My very first sentence said that the design of the GPIB bus does not support parallel operation.

[Dennis_Knutson]

What I should also add is that.my statement applies to different instruments. You can address multiple instruments at the same time using the low level GPIB functions. Not possible with VISA.