Hi John West , you made things very easy for me to understand
Actually , mapping that way is awesome , though it shows some errors
I am sure the general idea is fine , you've gave me the proper method
I made some modifications as bellow :
header=(uint8_t*)malloc(0x10); // header of the Nes file ...

Is there a common way to map the prg-rom ?
the following method works fine for the beginning of the buffer , but it doesn't give the right values at the end of the buffer

If the disassembler tells you that the program code begins at C000, it's because it is smart enough to read the two bytes at FFFC.

In the *.nes file, the 16 byte header is followed directly by the 16k PRG ROM, and you'll see towards the end of that 16k ROM the bytes
ffff ffff ffff ffff ff40 c0c0 ...

I am sure you are all completely right , the problem is that I am new to that stuff
I just cant understand why the disassembler gives me these results

may I ask you guys to have a look at that page and tell me if its any good ?

https://xem.github.io/nes/

I have attached the rom I am working on ...

What's the problem? You already have the answer in this thread.

You've mentioned that the reset-vector at $FFFC
but it was at $C000 according to the disassembler I've used

It's location is vary , each nes file has it's own location for it , and some are equal
I have to find a formula to find it ...

Thanks guys for your explanations

I make my conclusions as the following :

1. The 16 bytes of Nes header contains some information about the nes file (size of prg-rom , size of chr-rom , mappers , ...)
2. reset vector location is vary (I have no idea how to make my emulator get it)
3. prg-rom ...

The same data has to appear twice in the memory map, because that's how the machine works.

You are right
I have used a simple disassembler on my .nes file , I found the following :

Mapper
-------------------------------
NMI vector $C0C0
Reset vector $C000
IRQ vector $FFF9 ...

Hi BigEd 1. What I can understand of that is :
the 16k prog. data will start at $8000 and end at $C000

2. is the meaning of map it
put it at a new addresses ranges which are ($8000 - $C000) to be suitable for the 6502 nes system ?

I am totally lost , I have read the wiki that you've mentioned , also googled alot before and after posted my question
but I can't figure how a rom ends with address $6000, can be addressed with range $8000 and $c000 !

Hi Martin
your explanation is interested
is that the way how emulators get the start address of the program ?
I am currently working on a (mapper 0) rom , (no mapper ,no scrolling right now)
I just need to start with a simple emulator (currently the CPU)

I am still confused how addresses like ...

Still larger than my 24 kb rom addresses .

I am using a C compiler to read the entire rom inside a buffer byte array as the following :
rom = (unsigned char*) malloc (sizeof(unsigned char)*64001); // allocate enough space
fread (rom,sizeof(unsigned char),24592,fp); //
I checked my array compared to the hex editor , and it's fine , both are ...

Thanks for welcoming me :)
you are right
I opened it with a hex viewer , last address was 6000 , but that is in hexadecimal !
then it should be 24576 bytes , windows explorer says it is 24.0 KB (24,592 bytes)
I will check the link you've posted , I will be back soon , I need to ask some more ...

Hi everybody
I am new here
I am doing some basic work reading Nes rom , I've choosed a small size rom (Nuts & Milk) , which is 6000 bytes
I have read that the program's banks addresses are :
$8000 $4000 PRG-ROM
$C000 $4000 PRG-ROM

how that would be applicable on the rom I've mentioned above ?
any ...