Программирование AY - вопрос по огибающей

[Sinus]

да, инфа верняк (кстати, это же относится и к счётчикам каналов A, B и C).
ребята из mame проводили исследования:

Careful studies of the chip output prove that the chip counts up from 0
until the counter becomes greater or equal to the period. This is an
important difference when the program is rapidly changing the period to
modulate the sound. This is worthwhile noting, since the datasheets
say, that the chip counts down.
Also, note that period = 0 is the same as period = 1. This is mentioned
in the YM2203 data sheets. However, this does NOT apply to the Envelope
period. In that case, period = 0 is half as period = 1.

(вообще жутко всё серьёзно у них там в mame, аж завидно немного )