Hi Kashyap,

As far as I know the WDT cannot be disabled in a 1232 supervisor chip. But I am not sure of the IMP 1232. One simple way to feed the 1232 is from the ALE pulse and set the 1232 for maximum time out ( tie TD pin to Vcc) - why not try this ?

As Steve said the exact level of Vcc is very important.

Before giving up on the IC did you try checking if the ALE pulse is normal with a scope ? Also you can monitor the activity on the Reset pin with a scope. ( You can use the unused !Reset output of the 1232 via a transistor buffer to drive a LED and this will tell what the Reset is doing)

Normally I have found that issues like above prevent the IC from entering the programming mode rather than a fault with the IC. And once you have the Emergency escape route as outlined by Erik ( thanks to him), there is never a case of taking the chip to a parallel programmer to restore things. Just for your information I have enclosed the code snippet that will implement the Emergency Escape route. This has to be the first routine in code memory ( 0000H ) or at the location where your code starts.
<pre>
;***********************************************
;++ ~ENABLE BOOT VECTOR /89c51rd2 +++++++++++++
;***********************************************


BEGIN: JB P3.1, INIT_ALL ; If TxD is Low enter programming mode

WRSB: MOV AUXR1, #20H ;set the Enboot bit
MOV R0, #6 ;FOSC
MOV R1, #06H ;program status byte
MOV DPTR, #0000h ;specify status byte
MOV A, #0FFH ;Non zero status byte
CALL 0FFF0H ;execute the function


WRBV: MOV AUXR1, #20H ;set the Enboot bit
MOV R0, #6 ;FOsc
MOV R1, #06H ;program boot vector
MOV DPTR, #0001h ;specify boot vector
MOV A, #0FCH ;new value for the boot vector
CALL 0FFF0H ;execute the function

JMP $
</pre.

In the above the INIT_ALL, is the routine where your normal code begins.

Raghu