R08 and R16M file format

R08
2 Bytes per Frame
Byte 1: Player1
Byte 2: Player2

Bits        Hex     Buttons Pressed
00000000    00      no buttons pressed
11111111    ff      all buttons pressed

10000000    80   A Button
01000000    40   B Button
00100000    20   Select
00010000    10   Start
00001000    08   Dpad Up
00000100    04   Dpad Down
00000010    02   Dpad Left
00000001    01   Dpad Right

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R16M
16 Bytes per Frame
Byte 1,2: Player1-1
Byte 3,4: Player1-2
Byte 5,6: Player1-3
Byte 7,8: Player1-4
Byte 9,10: Player2-1
Byte 11,12: Player2-2
Byte 13,14: Player2-3
Byte 15,16: Player2-4

Bits                Hex    Buttons Pressed
00000000 00000000   0000   no buttons pressed
11111111 11111111   ffff   all buttons pressed
11111111 11110000   fff0   all normal buttons pressed

10000000 00000000   8000   B Button
01000000 00000000   4000   Y Button
00100000 00000000   2000   Select Button
00010000 00000000   1000   Start Button
00001000 00000000   0800   Dpad Up
00000100 00000000   0400   Dpad Down
00000010 00000000   0200   Dpad Left
00000001 00000000   0100   Dpad Right

00000000 10000000   0080   A Button
00000000 01000000   0040   X Button
00000000 00100000   0020   L Button
00000000 00010000   0010   R Button
00000000 00001000   0008   1 Button
00000000 00000100   0004   2 Button
00000000 00000010   0002   3 Button
00000000 00000001   0001   4 Button