What's the relation between ss:sp and extended BIOS(int 0x13, ah = 0x42)?

Question

If I don't initialized the the ss and sp or initialize correctly(for example ss:sp = 0xA000:0x0000), the code as below picture will not jump correctly.

boot sector

I want to copy 244 sectors from disk to memory by using extended BIOS interrupts(int 0x13, ah = 0x42, LBA).