Date: Thu, 7 Jun 2007 02:39:12 -0700 (PDT) From: Neil Bradley <nb@synthcom.com> Cc: arm@freebsd.org Subject: Re: 4-bit SD Card mode Message-ID: <20070607023728.X43808@synthcom.com> In-Reply-To: <53054.2001:6f8:101e:0:20e:cff:fe6d:6adb.1181203617.squirrel@webmail.alpha-tierchen.de> References: <50503.2001:6f8:101e:0:20e:cff:fe6d:6adb.1181202550.squirrel@webmail.alpha-tierchen.de> <20070607005128.T43808@synthcom.com> <53054.2001:6f8:101e:0:20e:cff:fe6d:6adb.1181203617.squirrel@webmail.alpha-tierchen.de>
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>> I've done SD drivers, both 1 and 4 bit, DMA and programmed I/O, on the
>> PXA270, Atmel SAM7, Atmel SAM9, and Freescale MX31 CPUs. How may I be of
>> assistance?
> Actually the driver does the whole status and error handling using an
> interrupt service routine. This is unsuitable in 4-bit mode because in
> this mode the interrupt line is shared with a data line. So to get 4-bit
> mode working it is necessary to know the complete definition of the
> "interrupt period" - the period where it is allowed to enable the
> interrupt during 4-bit mode.
Hm... I haven't ever heard of nor needed to consider such a thing in any
of my implementations. The controllers I've encountered all have a "1
bit/4 bit" mode setting, and as long as you tell the card to go in to 4
bit mode and set it in the hardware as well, the SD controller handles
everything for you.
What is the CPU in question?
-->Neil
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C. Neil Bradley - KE7IXP - The one eyed man in the land of the blind is not
king. He's a prisoner.
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