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List: ecos-bugs
Subject: [Bug 1001676] New: SPI cyg_spi_transaction_tick: Discrepancy between documentation and
From: bugzilla-daemon () bugs ! ecos ! sourceware ! org
Date: 2012-09-24 9:33:45
Message-ID: bug-1001676-777 () http ! bugs ! ecos ! sourceware ! org/
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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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