OPEN.BIN Build New File-to-open header

p1 = file header
p2 = file sector
p3 = num sectors
p4 = destination ptr

000699d4: 27bdffd8 addiu r29,r29,0xffd8
000699d8: afb00010 sw r16,0x0010(r29)
000699dc: 00808021 addu r16,r4,r0
000699e0: afb10014 sw r17,0x0014(r29)
000699e4: 00a08821 addu r17,r5,r0
000699e8: afb20018 sw r18,0x0018(r29)
000699ec: 00c09021 addu r18,r6,r0
000699f0: afb3001c sw r19,0x001c(r29)
000699f4: afbf0020 sw r31,0x0020(r29) 
000699f8: 0c01a68d jal 0x00069a34                    OPEN.BIN Open File <- if there's a file to open, make sure that's done first.
000699fc: 00e09821 addu r19,r7,r0
00069a00: 02002021 addu r4,r16,r0
00069a04: 02202821 addu r5,r17,r0
00069a08: 02403021 addu r6,r18,r0
00069a0c: 0c0046f4 jal 0x00011bd0                    Load Data From Disc (0x11bd0) (p1, p2, p3, p4) <- build file header & leave
00069a10: 02603821 addu r7,r19,r0
00069a14: 8fbf0020 lw r31,0x0020(r29)
00069a18: 8fb3001c lw r19,0x001c(r29)
00069a1c: 8fb20018 lw r18,0x0018(r29)
00069a20: 8fb10014 lw r17,0x0014(r29)
00069a24: 8fb00010 lw r16,0x0010(r29)
00069a28: 27bd0028 addiu r29,r29,0x0028
00069a2c: 03e00008 jr r31
00069a30: 00000000 nop