Talk:SGA
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32x File Format
I disassembled the nt.bin and subload.bin, looks like most of the decoding is done on the 68k side, rather than the sh2 (32x) side.
I will document my curiosities here, for others to read.
Special Values in decoding
If the y tile size is 11 then special values are 01 and 03, otherwise its 04 and 02. Havent found where its used yet. But those values pop up all over the compressed data.
LAB_0289: move #$0003,d3 ;6390: 363C0003 move #$0001,d4 ;6394: 383C0001 cmpi.b #$11,EXT_000D ;6398: 0C390011002018FF beq.s LAB_028A ;63A0: 6708 move #$0002,d3 ;63A2: 363C0002 move #$0004,d4 ;63A6: 383C0004 LAB_028A: rts ;63AA: 4E75
Possible code book setup
I think this code here is setting up a code book, whats interesting that it seeks to a specific location. Plus there is a specific code book size.
adda.l #$00003004,a0 ;6010: D1FC00003004 movea.l EXT_016B.w,a1 ;6016: 2278AA66 adda.l #$00003020,a1 ;601A: D3FC00003020 move #$1800,d0 ;6020: 303C1800 bsr LAB_0281 ;6024: 610001EC