Digital Multimeters (DMMs) and Precision DC Sources

cancel
Showing results for 
Search instead for 
Did you mean: 

PXIe-4139 Sequence Step Memory Depth

Solved!
Go to solution

Sequences are HW-controlled and deterministic so every step must be stored in the local memory.  For both regular and advanced sequences using the PXIe-4139, the maximum number of steps is not defined in the data sheet.  Maybe I missed it but I'm pretty sure it isn't there.  I searched for words like "step" and "memory" to no avail.

 

Anyways, what is the maximum number of steps I can add to a sequence regular sequence?  Does it change when advanced sequences are used?  Is it based on the the number of properties?

 

Thanks in advance.

0 Kudos
Message 1 of 5
(152 Views)

Recently we had the same problem. We tried to load over 10000 steps but an error returned.

As you know, there is no reference about maximum memory size.

 

Fortunately (but very tedious...), the error told us how much sequences could we load.

So my proposal is, run VI with large steps... Sorry for inconvenience...

Emboar
Certified LabVIEW Developer
There are only two ways to tell somebody thanks: Kudos and Marked Solutions

GCentral
0 Kudos
Message 2 of 5
(129 Views)
Solution
Accepted by jrasco

> Sequences are HW-controlled and deterministic so every step must be stored in the local memory.

 

If by "local memory" you mean "memory on the instrument", then you are incorrect. The NI-DCPower driver will compile the sequence steps (both regular and advanced) into the instructions that the hardware executes and streams them to the instrument as it runs.

 

A single step can result in wildly different number of these low-level instructions based on several factors such as: how many settings are being modified in the step, whether there is a range change involved, what state the hardware is in before the new step is executed, etc.

 

For these reasons, it doesn't make sense for there to be a "maximum number of steps" in the data sheet.

 

The maximum number of steps is limited by host (PC) memory. How much physical RAM do you have? How much physical RAM is in use and page-locked? Are you running in a 32-bit or 64-bit process?

 

Good luck!

 

Marcos Kirsch
Chief Software Engineer
NI Driver Software
0 Kudos
Message 3 of 5
(105 Views)

Marcos,

Thank you for the detailed reply.  I got the deterministic idea from this community post:

Configuring Advanced Sequencing - NI Community

Looks like I read too much into it.

 

0 Kudos
Message 4 of 5
(99 Views)

> Sequences are HW-controlled and deterministic

 

This part is true.

 

> so every step must be stored in the local memory.

 

This part is false. They are streamed to the instrument's memory where there is a buffer. As long as this buffer never underflows then all is good! The driver handles underflow conditions but they would only occur under extraordinary loads.

Marcos Kirsch
Chief Software Engineer
NI Driver Software
0 Kudos
Message 5 of 5
(95 Views)