- Konami Sound Cartridge
The Konami Sound Cartridge is supplied with the
MSX video games " Snatcher" and " Super Deform Snatcher". Sometimesit is known as the SCC+. It includes a slightly improved SCC sound chip and 64kB of volatile RAM. It is likely that the RAM was included since most MSX computers in Japanat the time of release had very little memory (mostly64kB).
Like the normal SCC, the chip has 5 audio channels. The waveform is set by 32 bytes of 8 bit samples. Each channel has its own 32 bytes of waveform, unlike the SCC where channel 4 and 5 share thewaveform.
The cartridge included with Snatcher is different than the one includedwith Super Deform Snatcher, but only in memory layout. It was probablydone to make it incompatible. Some MSX emulators emulate this cartridge,
Most video games on the Konami Games Collections for theMSX can use the cartridge that is included with Snatcher for better sound. Apart from those the Sound Cartridge is not used by any other programs.
The print on the chip is: "KONAMI 052539 SCC-I2312P001 JAPAN" followed bya fabrication location/date number, like 8951EAI. The first two digits are the year, followed by the week. The letters after that are some location/lot code.
It is possible to expand the memory to 128kB by adding 64kB of RAM to the cartridge. There are two open places on the PCB. When the RAM is added, bothtypes of cartridges become identical. The cartridge will work withboth "
Super Deform Snatcher" and " Snatcher" video games.
Surprisingly enough, a cartridge with 128kB RAM can behave exactly likea SCC
RROM cartridgeof 128kB. This means you can loadthose games into the RAM (eg. "Gradius 2", " F1 Spirit", " Quarth" and so on) and it will behave like the original ROM cartridge until the power is turned off, since it is volatile RAM. It is possiblethat this chip was originally developed for internal development andtesting use at Konami.
The RAM ICs are of type 4464. They are four bits wide and a 64K range. Theremight still some solder in the holes, you can use a solder sucker for that.
If you would like the cartridge to work with both video gamesthen you can also connect the memory banks (so they are mirrored). ConnectCAS (pin 16 of RAM IC) of one of the RAM ICs with one of the empty slots.
Using the memory
Everything is done using memory-mapped I/O and it is much like the
SCC ROM cartridges.
As with SCC cartridges, the memory is divided into fourmemory banks of 8kB:
; Bank 1 : 4000h - 5FFFh; Bank 2 : 6000h - 7FFFh; Bank 3 : 8000h - 9FFFh; Bank 4 : A000h - BFFFh
To change the mapping, write to one of these addresses:
; Bank 1 : 5000h - 57FFh; Bank 2 : 7000h - 77FFh; Bank 3 : 9000h - 97FFh; Bank 4 : B000h - B7FFh
Bits 3 through 7 are ignored. Values 0 to 7 select 8kB pages of the lower64kB (which is included with "
Snatcher") and values 8 to 15 the higher64kB (which is included with " Super Deform Snatcher").
By default (after reset) bank 1 selected area 0, bank 2 area 1, bank 3 area2 and bank 4 area 3. Again this is the same as SCC ROMcartridges. If the lower 64kB is empty (as it is with the Super Deform Snatcher cartridge) then the memory will be empty (reads FFh).
By default, the RAM cannot be changed. By setting a bit somewhere elsethe areas can no longer be changed (ROM mode) but can be written to (RAM mode). This is done by writing to the "mode register", which is alwaysaccessible through address BFFEh and BFFFh. The SCC can be put in also be put in SCC+ mode through this register, where channel 4 and 5 do not share a waveform.
; bit 7 : no function; bit 6 : no function; bit 5 : if set, sound chip is in SCC+ mode otherwise SCC compatibility; bit 4 : if set, banks 1 to 3 are in RAM mode otherwise area select; bit 3 : no function; bit 2 : if set and bit 5 reset, bank 3 is RAM mode irrespective of bit 4; bit 1 : if set, bank 2 is RAM mode irrespective of bit 4; bit 0 : if set, bank 1 is RAM mode irrespective of bit 4
Even in RAM mode the memory under BFFEh and BFFFh cannot be changed throughthose addresses as that will always end up in the mode register.
Konami uses 20h and 3Fh for the mode register as they always use SCC+mode. 30h would also work for RAM mode.
Using the sound chip
If bank 3 is in area select mode and bit 5 of mode register is reset, the SCC can be activated by writing 3Fh to one address 9000h through 97FFh. Thelayout is very similar to the SCC and the meaning ofthe registers is the same although the address differ somewhat and the waveform of channel 5 can be read. The SCC is visible at 9800h through 9FDFh.
Address read/write Function 9800h - 981Fh rw waveform channel 1 9820h - 983Fh rw waveform channel 2 9840h - 985Fh rw waveform channel 3 9860h - 987Fh rw read: waveform channel 4 write: waveform channel 4 and 5 9880h - 9881h w frequency channel 1 9882h - 9883h w frequency channel 2 9884h - 9885h w frequency channel 3 9886h - 9887h w frequency channel 4 9888h - 9889h w frequency channel 5 988Ah w volume channel 1 988Bh w volume channel 2 988Ch w volume channel 3 988Dh w volume channel 4 988Eh w volume channel 5 988Fh w on/off switch channel 1 to 5 9890h - 989Fh w same as 9880h to 988Fh 98A0h - 98BFh w waveform channel 5 98C0h - 98DFh rw deformation register 98E0h - 98FFh no function
If bank 4 is in area select mode and bit 5 of the mode register is set,the SCC+ can be activated by writing a value with bit 7 set to anywhereto B000h through B7FFh. Now the SCC+ becomes active at B800h throughBFDFh.
Address read/write Function B800h - B81Fh rw waveform channel 1 B820h - B83Fh rw waveform channel 2 B840h - B85Fh rw waveform channel 3 B860h - B87Fh rw waveform channel 4 B880h - B89Fh rw waveform channel 5 B8A0h - B8A1h w frequency channel 1 B8A2h - B8A3h w frequency channel 2 B8A4h - B8A5h w frequency channel 3 B8A6h - B8A7h w frequency channel 4 B8A8h - B8A9h w frequency channel 5 B8AAh w volume channel 1 B8ABh w volume channel 2 B8ACh w volume channel 3 B8ADh w volume channel 4 B8AEh w volume channel 5 B8AFh w on/off switch channel 1 to 5 B8B0h - B8BFh w same as B8A0h to B8AFh B8C0h - B8DFh rw deformation register B8E0h - B8FFh no function
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