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From: bugzilla-daemon@bugs.ecos.sourceware.org
To: ecos-bugs@ecos.sourceware.org
Subject: [Bug 1001676] New: SPI cyg_spi_transaction_tick: Discrepancy between
 documentation and
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Date: Mon, 24 Sep 2012 09:34:00 -0000
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           Summary: SPI cyg_spi_transaction_tick: Discrepancy between
                    documentation and
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: low
         Component: SPI
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: ilijak@siva.com.mk
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


There is a discrepancy between Reference Manual (RM) and implementation of most
SPI drivers regarding SPI chip select behaviour during cyg_spi_tick.

The SPI part of RM states (underlines by reporter):

"... If the device requires additional clock ticks in the middle of a
transaction without being selected, cyg_spi_transaction_tick can be used.
_This_will_drop_the_device's_chip_select_if_necessary, then generate the
appropriate number of ticks. The arguments are the same as for cyg_spi_tick.
..."

And about cyg_spi_tick:

"... These ticks must happen at the appropriate clock rate
_but_no_chip_select_should_be_asserted_ and no data transfer will happen.
cyg_spi_tick provides this functionality. ..."

Contrary to this, most of the actual drivers do not touch the chip selects.

Ilija

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