XL208 SPI slave boot

Technical discussions around xCORE processors (e.g. General Purpose (L/G), xCORE-USB, xCORE-Analog, xCORE-XA).
aelder
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XL208 SPI slave boot

Postby aelder » Tue Mar 20, 2018 1:29 pm

Datasheet for XS2-L8A-256-TQ64 section 8.3 describes boot from SPI slave, but app note AN00238 states that SPI slave boot is limited to XL218 devices. Which is it? Is the datasheet wrong?
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mon2
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Postby mon2 » Wed Mar 21, 2018 12:58 pm

Hi. Think the confusion is on the frame of reference.

Section 8.3 of the datasheet is common to all XMOS processors and details how to boot firmware using a SPI slave device that will be an external standard SPI flash. If you can, consider to use QSPI mode for booting these XCORE-200 devices which will boot your firmware faster. The MODE pins will need to be strapped accordingly if you wish to use QSPI or standard SPI (slower). From the excellent support received by the factory, highly recommend the ISSI brand. There is a very long thread on this forum where ISSI assisted to debug a boot issue with the XMOS processors.

Now the AN00238 appnote is on how to take the XMOS CPU and make it look like a SPI SLAVE. Once done, you should be able to mate the finished project (XMOS based) to an external SPI Master and this XMOS CPU will act "like a flash memory device". That is my understanding of the difference.

Summary: Believe you after the use a local SPI flash device to boot your firmware - that is common to any XMOS processor you choose. The XCORE-200 series are a better choice. Some modes like the XUF series feature an internal flash device inside the package.

Hope this helps.
aelder
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Postby aelder » Wed Mar 21, 2018 1:07 pm

Thanks for the feedback and the ISSI comment.

So, an XCORE-200 XL208 device can be booted as an SPI slave by another processor? Or, not?
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mon2
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Postby mon2 » Wed Mar 21, 2018 1:41 pm

So, an XCORE-200 XL208 device can be booted as an SPI slave by another processor? Or, not?


Do not see any reason why the XL208 will not work as an SPI slave.

The same appnote states:

xCORE-200 devices also have a SPI slave boot mode.

so any XCORE-200 processor will be suitable for this project. Guessing the XL216 is cited as this processor is on the XCORE-200 Explorer kit.

XL208 = 2 tile processor with 8 logical cores per tile.
XL216 = 2 tile processor with 16 logical cores per tile.

Do review Figure 9 inside each respective datasheet where it shows (XL216):

Image

but for XL208:

Image

Not sure why this difference is there (XL208 does not show the Tile 1 boot option with SPI SLAVE mode). To be clear, best for you to goto xmos.com and create a technical support ticket for their staff to respond. This is a very interesting topic so do post your results. On a positive note, the pinout is the same between the processors so if really required, you could migrate your XL208 design to be XL216 but wondering if the missing details of figure 9 in the XL208 is in error. That is, why is Slave Boot for Tile 1 not mentioned inside the XL208 / XU208 datasheets?? Have not used such a configuration to date so cannot comment on this.

A bit off topic but assuming that you are considering the XL208 over the XL216 as a cost reduction? Do shop around as we found that sometimes the more popular processors with even more features can be sourced for lower costs. For example, XE216, etc. Check Future Electronics who was more competitive on past processor costs vs. Digikey.
aelder
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Postby aelder » Wed Mar 21, 2018 2:09 pm

Thanks for the comments. I'll open a support ticket.
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mon2
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Postby mon2 » Thu Mar 22, 2018 2:05 pm

Oh boy. My bad...

the XL208 is a SINGLE TILE CPU with 8 cores.

the XL216 is a DUAL TILE CPU with 8 cores per tile.

This explains why Tile 1 is not shown on the XL208 as there is only Tile 0 (ie. single tile). Sorry about that...
aelder
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Postby aelder » Thu Mar 22, 2018 8:47 pm

No worries. I figured it was just a typo!
davidb
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Postby davidb » Wed Mar 28, 2018 10:15 am

Hi Just to provide some clarification.

The datasheet is the document to work from regarding what features are supported, e.g. SPI on a single tile 0.

This particular apps note (AN00238) is for a 2 tile device.

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