Если коротко, то вот основная инфа по SCC:
Код:
SCC FUNCTIONS
-------------
The SCC has 4 different functions :-WAVEFORM (32 bytes)
-FREQUENCY (12 bits)
-VOLUME ( 4 bits)
-KEYON ( 5 bits)
WAVEFORM
--------
This is the form of the wave that is used for generating the sound.
It consists of 32 bytes that can be designated in any way you like.
If the soundprocessor has read byte #31 it will again start with byte #0
The meaning of each byte can be understod with the figure below.
7f | - ------
| - - -
| - - -
1 | - ---
0 ----------------------------|31
ff | -
| -
| -
80 |-
0-&h7f = 0 tot 127
&H80-&hff = -127 tot -1
If the SCC is in page 2 the following addresses are used for the waveform.
channel 0 &h9800-&h981f
channel 1 &h9829-&h983f
channel 2 &h9840-&h985f
channel 3+4 &h9860-&h987f
As you can see channel 4 has no waveform of it's own but uses
the wave form of channel 3
Frequency
----------
The frequency of the SCC consists out of 12 bits and is calculated
in the same way as the frequency of the PSG.
3579545
The formula : value = --------------
(16*freq)
The minimal value has to be 16 and the maximun value is 4095
The value of the frequency has to be written to the following addresses
LSB (8bit) MSB (4bit)
channel 0 &H9880 &H9881
channel 1 &H9882 &H9883
channel 2 &H9884 &H9885
channel 3 &H9886 &H9887
channel 4 &H9888 &H9889
VOLUME
------
Also this is the same as the PSG, a 4bit value
&B0000 = soft
&B1111 = loud
The values of the volume has to be written to the following addresses
channel 0 &H988a
channel 1 &H988b
channel 2 &H988c
channel 3 &H988d
channel 4 &H988e
KEYON
-----
With this function the generation of sound is enabled or disabled.
The keyon data for each channel is in just 1 byte:
b7 b6 b5 b4 b3 b2 b1 b0
X X X channel4 channel3 channel2 channel1 channel0
This byte is on address &H988F