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Diffstat (limited to 'doc/esf.txt')
| -rw-r--r-- | doc/esf.txt | 58 |
1 files changed, 40 insertions, 18 deletions
diff --git a/doc/esf.txt b/doc/esf.txt index 7fbe73e..ab74399 100644 --- a/doc/esf.txt +++ b/doc/esf.txt @@ -217,34 +217,56 @@ $2Bnn: Set volume PSG channel #4 ============================================================================= -$30nnnn: Set frequency FM channel #1 -$31nnnn: Set frequency FM channel #2 -$32nnnn: Set frequency FM channel #3 -$34nnnn: Set frequency FM channel #4 -$35nnnn: Set frequency FM channel #5 -$36nnnn: Set frequency FM channel #6 +$30nn/$30nnnn: Set frequency FM channel #1 +$31nn/$31nnnn: Set frequency FM channel #2 +$32nn/$32nnnn: Set frequency FM channel #3 +$34nn/$34nnnn: Set frequency FM channel #4 +$35nn/$35nnnn: Set frequency FM channel #5 +$36nn/$36nnnn: Set frequency FM channel #6 These events set the raw frequency of a specific FM channel, without - triggering a new note. Meant for note slides. The following two bytes - specify the new frequency in the same format as the YM2612 expects. The - first byte is register +$A4, the second byte is register +$A0. - + triggering a new note. Meant for note slides. The format of this event + depends on whether the second byte has its MSB set or not. + + If the 2nd byte's MSB is set, the event is two bytes long. The 2nd byte + is the semitone in this format (where "octave" is from 0 to 7 and + "semitone" is from 0 to 11): + + octave * 16 + semitone + 128 + + If the 2nd byte's MSB is clear, the event is three bytes long. The 2nd + and 3rd bytes specify the new frequency in the same format as the YM2612 + expects. The 2nd byte is register $A4+, the 3rd byte is register $A0+. + Echo uses the following frequency values for each semitone: - + C - 644 | E - 810 | G# - 1021 C# - 681 | F - 858 | A - 1081 D - 722 | F# - 910 | A# - 1146 D# - 765 | G - 964 | B - 1214 -$38nnnn: Set frequency PSG channel #1 -$39nnnn: Set frequency PSG channel #2 -$3Annnn: Set frequency PSG channel #3 +$38nn/$38nnnn: Set frequency PSG channel #1 +$39nn/$39nnnn: Set frequency PSG channel #2 +$3Ann/$3Annnn: Set frequency PSG channel #3 These events set the raw frequency of a specific square wave PSG channel, - without triggering a new note. Meant for note slides. The following two - bytes specify the new frequency, the first byte containing the four least - significant bits (LSB aligned), and the next byte containing the six most - significant bits (LSB aligned too). + without triggering a new note. Meant for note slides. The format of this + event depends on whether the second byte has its MSB set or not. + + If the 2nd byte's MSB is set, the event is two bytes long. The 2nd byte + is the semitone in this format (where "octave" is from 0 to 5 and + "semitone" is from 0 to 11): + + octave * 12 + semitone + 128 + + If the 2nd byte's MSB is clear, the event is three bytes long. The 2nd + and 3rd bytes specify the new frequency, the 2nd byte containing the + four least significant bits (LSB aligned), and the 3rd byte containing + the six most significant bits (LSB aligned too). + + IMPORTANT: using the 3-byte event prevents semitone shifting in PSG + instruments from working. It will start working again whenever a new note + or the 2-byte version of this event is used. Echo uses the following frequency values for each semitone: |