Experimental Physics and
Industrial Control System

Hi Eric,

 

1. Yes, I have recently done quite some work on this issue (hopefully I will talk about it in EPICS meeting).

 

2. The bandwidth you get depends on the hardware of course. I tried it on a SIS3302 ADC from Struck with mvme-6100 and mvme-4100 SBC’s (vxWorks OS). In the best case I could get like 85 MB/s. The guys in Struck told me that the highest rate they have measured is about 90 MB/s but they use a special self-developed PCI/cPCI-VME interface card to read the data.

 

3. Yes, mvme-6100 and mvme-3100 BSP’s have a usable driver (much better than mvme-5100 / 2300) but you have still to do some work. First issue is that you have to set the right transfer protocol for the VME (outbound) window in use. If you always use the same protocol (very unlikely!) you can hard code this only once in the BSP but if you have boards with different protocols e.g. MBLT, 2eVME, etc. then you have to be able to set the protocol of the corresponding window dynamically at runtime. Second issue is that the API provided with the out-of-the-box BSP is single-requester; meaning that while one DMA transfer is executing the second transfer request is not accepted. Therefore the application program has to keep retrying until his request gets accepted (at some time when DMA engine is not busy).

 

I have written a (BSP) driver on top of the existing routines which addresses above mentioned problems. We also use the same API for all our SBC’s (mevme-6100, 4100, 5100, 2300 series) to ease writing and maintaining our drivers/application programs.  

 

Regards,

Babak

 

PS: you may get a little bit better rates by disabling the caching/snooping in the BSP but you have to then take care of data consistency too.