Hot!dsPIC33CK256M508 family SPI SSx pins not labeled

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2018/09/13 21:10:31 (permalink)
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dsPIC33CK256M508 family SPI SSx pins not labeled

The SPI ports have highest speed when used on their hardware wired ports, but the SSx pins for these ports are not shown anywhere, what are their pin numbers?
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    qhb
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/13 21:22:58 (permalink)
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    It's only SPI2 that can use direct pins.
    I suspect it's only SCK2/SDO2/SDI2 that matter, and SS2 can use PPS.
    I agree that TABLE 1-1 has a "(3)" footnote on "SS2" as well, implying that there should also be a dedicated version of that pin. I think that's probably a datasheet mistake.
     

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    engineering@skutchelectronics.com
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/13 22:55:12 (permalink)
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    As a side note, it also doesn't show the hard pin mapping for SPI1 and 3, which is needed to get the 40Mhz clock rate.
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    qhb
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/13 23:07:30 (permalink)
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    There is no hard pin mapping for SPI1 or 3.
    Where are you reading that there is?
    There is one discrepancy in the datasheet, in that it mentions "50 MHz" for SPI2 at the start of the SPI chapter, but only "40 MHz" in the AC timing specs at the end, for "SPIx dedicated pins".
    That does not mean that every SPI port has dedicated pins.
     

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    engineering@skutchelectronics.com
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/14 10:56:16 (permalink)
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    The hard wired pins seemed implied by the description on the web page that said "3 4-wire SPI/I2S up to 40 MHz with dedicated pins"; a very poorly worded statement apparently, and with the majority of the family only working up to 15 Mhz, that's an understandable conclusion.
    The 50 Mhz comes from the manual, page 373 "On 48, 64 and 80-pin devices, SPI instance SPI2 can work up to 50  MHz speed when selected as a non-PPS pin."  The only problem is the SS2 pin doesn't seem to be mapped to a hard pin, so does that mean the port can still work at 50 Mhz if I map the SS2 pin to one of the RPx pins?
     
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    marcov
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/14 11:46:07 (permalink)
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    Maybe it can, since ss doesn't need such a high frequency, since it doesn't toggle on every bit like sdi/o/ck.
     
     
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    MBedder
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/14 11:48:33 (permalink)
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    "Highly likely" yes since the SS pin toggling frequency is at least 8 times lower than SCLK/SDx toggling frequencies.
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    engineering@skutchelectronics.com
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/14 12:53:14 (permalink)
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    Thanks, that makes reasonable sense.  It'd be great if they would update the datasheets, but I can understand that might be an enormous task with all of the products they have now; maybe some day...
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    Aussie Susan
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    Re: dsPIC33CK256M508 family SPI SSx pins not labeled 2018/09/16 19:42:04 (permalink)
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    Check out comment #3 at the bottom of Page 19 of the data sheet where it states that SPI2 supports dedicated pins on certain hardware configurations. This is controlled by the SPI2PIN bit in the FDEVOPT config word.
    Are you using a 48- or higher pin package?
    Susan
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