port 0 "extended memory"
bits D0 - D3 swtch 32k pages 32Kb
page 0 - ROM
bits D4 - D7 - reserved

ports 1 - 5 "support connection to Spectrum"

port 1
Read of command by General Sound
D0 - D7   - command code

port 2
Read of data by GS
D0 - D7   - data 

port 3
Record of data by GS for Spectrum
D0 - D7   - data

port 4
Read of status word by GS
D0  - command flag
D7  - data flag

port 5
Resets bit D0 (command flag) of status word

ports 6 - 9 "volume setting"
in channels 1 - 4
D0 - D5  - volume
D6,D7  - reserved

port 
Sets bit D7 of status word non-equal to bit D0 of port 0

port B
Sets bit D0 of status word equal to bit D5 of port 6

                        Memory map

#0000 - #3FFF  -  first 16Kb of ROM
#4000 - #7FFF  -  first 16Kb of first RAM page
#8000 - #FFFF  -  switcheable 32k pages
                  page 0  - ROM,
                  page 1  - first RAM page
                  page 2... RAM


Data are in channels are stored automatically when CPU read RAM on addresses
#6000 - #7FFF
Channels` data should be placed on the following addresses:
ͻ
bit of addres  for channel     #6000 - #60FF  - data of channel 1
             Ķ   #6100 - #61FF  - data of channel 2
              1  2  3  4    #6200 - #62FF  - data of channel 3
Ķ   #6300 - #63FF  - data of channel 4
  A0 - A7     X  X  X  X    #6400 - #64FF  - data of channel 1
                                           .
     A8       0  1  0  1                   .
                                           .
     A9       0  0  1  1                   .
                                           .
  A10-A12     X  X  X  X                   .
                                           .
  A13,A14     1  1  1  1                   .
                                           .
    A15       0  0  0  0    #7D00 - #7DFF  - data of channel 2
                            #7E00 - #7EFF  - data of channel 3
ͼ   #7F00 - #7FFF  - data of channel 4
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