HSC Layout

Atari 7800 HSC NVRAM Layout

1000	00	00	68	83	aa	55	9c	00	00	01	03	1f	00	00	00	00
1010	00	00	00	00	00	00	00	00	00	00	00	00	00	00	00	00
1020	00	00	00	00	00	00	00	00	03	ff	ff	ff	ff	ff	ff	ff
1030	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1040	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1050	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1060	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	23	8a	ff	ff
1070	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1080	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1090	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
10a0	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
10b0	ff	23	0f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
10c0	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
10d0	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
10e0	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
10f0	7f	7f	7f	7f	7f	7f	04	04	7f	7f	7f	7f	7f	7f	7f	7f
1100	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
1110	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
1120	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f
1130	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	7f	01	02	ff	ff	ff
1140	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1150	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
.....	..	..	..	..	..	..	..	..	..	..	..	..	..	..	..	..
1780	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
1790	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
17a0	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
17b0	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff	ff
17c0	ff	ff	ff	ff	ff	ff	ff	ff	00	43	34	08	00	da	9a	00
17d0	00	00	da	9a	00	00	00	da	9a	00	00	00	da	9a	00	00
17e0	00	00	43	75	00	00	da	9a	00	00	00	da	9a	00	00	00
17f0	da	9a	00	00	00	da	9a	00	00	00	da	9a	00	00	00	ff

color	purpose	size
	backup for zp94 and zp95	2 bytes
	cart magic number	5 bytes
	current function ID	1 byte
	cart owner name	32 bytes
	cart owner name length	1 byte
	game ID table, byte 1	69 bytes
	game ID table, byte 2	69 bytes
	game difficulty level table	69 bytes
	game index table	69 bytes
	game save entries table	25 x 69 bytes
	temp score entry	5 bytes
	unused	1 byte

Notes:

• The above pictured data is for 2 games: Xevious (ID: $2323) and FoodFight (ID:$8A0F), each with a single difficulty=4 save.
• If any of the magic numbers are wrong, the HSC is assumed to be corrupted and will be reformatted the next time an official HSC game is played.
• All tables have 69 entries, and are populated from back to front.
• If you wish to make your own save on an initialized HSC without using the HSC routines, you need to make a new entry in the 2 game ID tables, the difficulty table, and the index table. The game index table entries should be rewritten to all be consecutive.
• The 3 high score initials are encoded with 5 bits each, consolidated into 2 bytes, in the form 22211111 22-33333