external WDT for msp

Please be a little more specific.

Why do you want to use an external watchdog? All the MSP430s already have a watchdog timer built in.

Alexander Mykyta said:

All the MSP430s already have a watchdog timer built in

IIRC On the old 1x family, it was possible to cut-off the MSP from its clock. Also, these chips did not have a voltage supervisor.
So when I took over some already started MSP projects, a combined voltage supervisor/watchdog chip was attached to these MSPs (specifically the MSP430F1232).

On newer MSPs, neither function should be necessary externally. But if someone wants... We used teh TC1232, sine the primary power supply was 5V and the watchdog therefore triggered before the 3.6V began to drop. However, an external watchdog makes problems when programming, since durign programming time, it is not served and will cause unexpected resets. (On my first design update, I introduced a 10k series resistor between watchdog and RST, and the programmer had a 4,7k pullup to override the watchdog if connected)

Chandrasekhar N said:

I am trying to adapt an external watchdog timer

What do you mean by, "adapt" here? Do you have some existing circuit that you're working from?

 

Chandrasekhar N said:

for my MSP430f5438.

As already noted, the MSP430f5438 has an internal watchdog - why do you want to add an external one?

 i dont know from where to start.

Do you understand the basics of what Watchdog timers do, and what they're for?

And please suggest few ICs for the same.

What searching have you done so far?