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Function 55 and its subfunction 55

Subfunction 55 - Start playing data on the built-in speaker

Options:

· eax = 55 - function number

· ebx = 55 - subfunction number

· esi = data pointer

Return value:

· eax = 0 - successful

· eax = 55 - error (speaker is disabled or busy)

Data is an array of variable-length elements. The format of each element is determined by the first byte:

· 0 = end of data

· 1..0x80 = sets the duration of the sound in hundredths of a second of a note, determined by the immediate frequency value

o the next word (2 bytes) contains a frequency divider; frequency is defined as 1193180 / divider

· 0x81 = invalid

· 0x82..0xFF = note, defined by octave and number:

o duration in hundredths of a second = (first byte) -0x81

o there is one more byte;

o (second byte) = 0xFF - pause

o otherwise, it has the form a * 0x10 + b, where b = note number in octave from 1 to 12, a = octave number (counting from 0)

Remarks:

· Speaker eating may be prohibited / enabled by function 8 subfunction 8.

· The function returns control, informing where the request information should go. The playback itself is independent of the program.

· Data should be stored in memory at least until the end of playback.

Constants for registers:

eax - SF_SPEAKER_PLAY (55)