Dear All,
We have created a custom OS, which boots form Hard Disk (as usual ). We now need to detect the USB and its contents.

So far we are able to read the MBR and Master Partition Table(MPT)of USB using INT13/AH=02

Can somebody help one below queries:
1) In MPT CHS value was 0,1,1 which gave the BPB. Now how to locate the FAT & Root Directory using this information. Also should we read using INT13/Ah=02 (CHS method) OR INT13/AH=42 (Using LBA)

2) We are using USB of 2GB, do we neeed to check for extension interrupts 41h & 42h to read the USB data.

3) How to setup the DAP ofr Ah=42.

It will be helpfull if a sample assembly code is provided.

Thanks & Regards,