[U-Boot-Users] Loads function and flow control.
wd at denx.de
Mon May 26 17:34:08 CEST 2003
In message <20030526150145.GO24207 at pengutronix.de> you wrote:
> On Mon, May 26, 2003 at 04:46:05PM +0200, Wolfgang Denk wrote:
[about flow control]
> > No there is none, and there is no need for one.
> ... as the kermit protocol ensures that packets with incorrect checksums
> are resent.
Flow control and checksums address two different kinds of problems.
While checksumming can detect the effects of overrun problems, flow
control cannot solve the other problems that can cause checksum
So far, in all cases I have seen with U-Boot (including the pre-
decessor projects PPCBoot and ARMBoot) the CPUs were fast enought o
easily handle serial downloads using both "loadb" and "loads" at
least at 115200 bps. Without any need for flow control.
> > I don't think so. Even at high baud rates (like 115200 bps) there is
> > more than enough time to receive characters through the serial line -
> > remember that U-Boot is strictly single-tasking, so the CPU has
> > nothing better to do but to wait for characters.
> Nevertheless there may be situations where for example cables make
> problems, so using a mechanism which checks if the data is correct is
> not the worst idea.
But this has nothing to do with flow control.
You are right, a protocol with error checking and recovery (like
kermit binary protocol) _is_ superior to a protocol without or no
protocol at all - but this was not the topic here.
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
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