DRAM vs OCRAM for SDMA<->MPCore Data Exchange

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DRAM vs OCRAM for SDMA<->MPCore Data Exchange

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rolfw
Contributor I

In the context of a high performance bidirectional data exchange between Cortex-A9 MPCore and the SDMA via FU Bursts (using custom SDMA scripts connecting to peripherals), there's non-cached memory needed. Is there any advantage of using OCRAM instead of external DRAM?

For ex. when massive concurrent DRAM writes happen from other A9 cores? I know that NIC-301 handles arbitration of DRAM access and gives SDMA already a better QoS than MPCore, but looking at the NIC-301 chapter in the IMX6QD tech ref, figure 45-1 on p 4012 hints at using the OCRAM for "multimedia" purpose. Since I'm not using any PCIe, FAST3 would be exclusively then used for OCRAM and maybe of advantage than going into arbitration on FAST2 for DRAM?

What I am trying to achieve is a quite massive, stable, un-interrupted bidirectional stream of multiple SSIs to/from MPCore using SDMA. So, from a bus perspective, would using OCRAM for non-cached exchange buffers be preferable over DRAM?

Thanks

Rolf

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igorpadykov
NXP Employee
NXP Employee

Hi Rolf

I think you are right that for un-interrupted bidirectional stream of multiple SSIs to/from MPCore using
SDMA using OCRAM would be preferable over DRAM. Note that OCRAM operating frequency is 133MHz
according to Table 18-3,18-4 i.MX6DQ RM.
http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf

Best regards
igor
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