XRAM not cleared, variables not assigned

"My guess is that you need modify startup.a51 to select internal RAM as the very first thing."

Yes - Note that the memory settings in uVision do not generate any code to configure the target processor. You have to add that manually - and startup.a51 would be a very good place to do it.

"My guess is that you need modify startup.a51 to select internal RAM as the very first thing."

Yes - Note that the memory settings in uVision do not generate any code to configure the target processor. You have to add that manually - and startup.a51 would be a very good place to do it.

iv modified startup.a51 as iv shown in my first post. are there any more changes i need to make??

i got the program to work on an evaluation board using the internal ram. variable assignment is not taking place only during declaration as follows

unsigned char InitOver[3]={0,0,0};

the value of InitOver[0] is being set to D7. however if i assign a value to it during the program, it works fine.

secondly, though it is working on the evaluation board, it refuses to call any functions on my final project board. i have a loop as follows:

while (1)
{
MODBUS_RTU_SLAVE(&Modbus);
}

however the MODBUS_RTU_SLAVE function is not called. i check this by toggling P1^0 on entering the function. P1^0 is being pulled high thru a DIP switch. on the evaluation board, i have an LCD display, so i can display a value on it on entering the function which it does perfectly. on my board, the display init function is commented

From the C51 manual:

The INIT.A51 file contains the initialization routine for variables that were
explicitly initialized.

;  INIT.A51:  This code is executed, if the application program contains
;             initialized variables at file level.

; This section describes the initialization data generated by C51 for
; explicit variable initializations (in segment ?C_INITSEC).
;
; Explicit variable initilizations at C source level are stored by C51 in
; the segment ?C_INITSEC.  All partial segments are combined at linker level
; to one segment.  The segment end value DB 0 is taken from this library module
; INIT.A51.
;

thanks...il try doing that for the variable assignment. however the variables not getting assigned is of no significance if the function itself is not called.

i am passing the address of a structure to the function. the contents of thi structure "Modbus" contain basic settings for my program conditional statements. these variables are being assigned.

also doesnt the INIT.A51 procedure apply even if i use off chip xram?? because INIT.A51 was not a part of my project till now. and the program worked without a hitch

The physical location of the "external" RAM doesn't matter. It's called "external" because of the design of the original 8051. Often, you have "external" RAM integrated onto the same die as the processor core and sold in a single package, but as far as the processor core is concerned, it's still "external". Xdata really means "not the 128/256 bytes of directly/indirectly addressable RAM that you can only access via the DPTR by using a MOVX instruction.".

If you have both sorts of memory, then there's likely some part-specific registers you initialize to select whether you're using the on-chip xdata or the off-chip xdata. Earlier posts discuss that.

Since the initializer shown above is { 0, 0, 0 }, it doesn't really matter for this case if you leave out INIT.A51. The memory will be initialized to 0 by the STARTUP.A51 code anyway.

"If you have both sorts of memory, then there's likely some part-specific registers you initialize to select whether you're using the on-chip xdata or the off-chip xdata."

Yes - that's why I said earlier,

"Note that the memory settings in uVision do not generate any code to configure the target processor. You have to add that manually - and startup.a51 would be a very good place to do it."

thanks all u guys for helping out...started searching for the startup.a51 additions and found this:

http://www.keil.com/support/docs/1978.htm

solves my problem...also understood the need (or the lack of it in my case) for init.a51

thanks once again