Lpc2000

It's probably not much help to you, but we specifically don't use 
the DCD line in a connection to a modem for this very reason.

In other words, if there's even a chance that something connected to 
the line can fool the part into thinking it's being requested to 
enter bootloader mode, then you're best not to connect it. As you 
point out, there are failure modes that can lead to an unrecoverable 
state (in the field).

We connect all modem signals (RTS/CTS/RI etc.) as normal, but 
connect the DCD to an external interrupt line instead of the DCD 
line on the LPC part, and modify the UART driver software 
accordingly. If this isn't an option (i.e. you've finalised your 
hardware design, or you're really short on pins), then there is one 
possibility you can look at: if the (internal) watchdog resets the 
device, the external request to enter the boot-loader is ignored. 
You can probably make use of this to come up with a scheme for 
improving the situation.

However, it's difficult to see how you could prevent the lockout 
situation when an external reset is applied whilst a modem DCD is 
being asserted. Power fails are less of an issue: presumably the 
modem is powered off the same source, in which case DCD will be de-
asserted on power-up (unless there's some modem that can establish a 
connection in less than 3ms?). 

I doubt Philips would modify the boot-loader in such a way as you 
propose: there could be unintended side effects for parts already 
deployed if they did.

Sorry not to be of more help: I'd be interested to hear if you come 
up with some other suggestions.

Brendan

--- In lpc2000@yahoogroups.com, "misstero" <suriyant@...> wrote:
>
> Dear All,
> 
> I have design which is connected modem signals to UART1 (Full 
UART) of
> LPC2xxxx but I found serious problem with DCD signal.
> 
> DCD signal of UART1 is alternate function on P0.14 which is LPC2xxx
> bootloader determine during reset to go into Bootloader mode if it 
low.
> 
> Our problem occur when modem connected that DCD is active (Active 
Low
> same as bootloader mode request) and LPC2xxx is reseted which may
> cause by unstable power or external reset via RESET pin by
> supervisory. This made LPC2xxx  go into bootloader mode forever 
cannot
> return back to our application code even modem's DCD inactive 
later.
> Only power cycle both LPC2xxx and modem to restart it to 
application
> code. This case unaccetable when devices are installed in unman 
location.
> 
> I have an idea to solve this problem but it need help from Philips 
by
> add time-out in Bootloader mode if it does not have any activity 
for
> short period of time (etc. 3s) it should be retry to execute
> application code repeatly so I'd like to ask Philips is it 
possible?
> 
> Anyone have other ideas to solve this problem? Please share with 
me. I
> prefer to solve by software first if it possible.
> 
> Thanks,
> Suriyan.
>