At offset 0x21 (33), it loads the offset for the bitmap data in the cartridge into one register, and the address for tile data RAM into another. Offsets 0x27-0x32 are a loop that calls out to functions at offsets 0x95-0xa7 and 0x96-0xa7 to double up the bits and scale the image to 2x its original size. After the code to scroll the logo, it plays the iconic double-ping sound.
At offset 0xE0, it loads offsets for the firmware copy of the logo and the cartridge copy of the logo. 0xe6-0xef iterate through the logo. If at any point the 2 copies don't match, there's a jump at offset 0xe9. Here's the relevant part of the loop:
LD A, (DE) ;Load a byte from the cartridge copy
INC DE ;Increment the pointer to the next byte
CP (HL) ;Compare A with the byte at (HL)
JR NZ, -2 ;If not equal, lock up by jumping back to this location
The patent actually covers this on page 7: https://patentimages.storage.googleapis.com/77/c0/90/d2c7514...
And claims 14+15 seem pertinent:
> 14. A hand-held electronic game machine in accordance with claim 9, wherein said processing means includes detecting means responsive to a connected external memory for detecting whether said connected external memory is an authorized or unauthorized memory.
> 15. A hand-held electronic game machine in accordance with claim 14 wherein the processing means includes further means responsive to said detecting means for preventing an unauthorized external memory from being used for executing a game program.
There's some good commentary on the legal situation, and its relation to Sega's similar legal theories (as regarded the Genesis/MegaDrive) on TVTropes (although it's a bit short):
http://tvtropes.org/pmwiki/pmwiki.php/CopyProtection/Nintend...
