★ HARDWARE ★ PERIPHERIQUES ★ CPC-Digiblaster v2.0 ★ |
| Sound - Digiblaster v2 | Hardware Peripheriques |
The original Text was written by A.Stroiczek and the DMV-Verlag (CPC International 8/9'91), the hardwarelayout of the Digiblaster v2.0 was performed by Joshua/Exodus and converted by Tim Riemann (TCS-Software@gmx.de). Please mail me if there are any mistakes (especially my bad english ;-) ! If we're looking at the 16bit computers like Amiga, Atari ST, Mac and PC (with a soundcard) the CPC users can be jealous. We can help with an easy circuit plan. The CPC only can do rectangle frequencies. Amiga and other computers are working with digital instruments which they give out with internal D/A converters. If you look exactly the CPC has the possibility to give out digital instruments. For this you need the volume register. This register can handle 16 different volumes. So it may be possible to play samples with 4bit. But the soundchip dissapoints again. To play a linear volumeincrease the power at the sound port is logarithmical. This means that you have to change the values so that they are linear. So you only have 3bit. The Amiga has a advantage with his 8bit samples. If you say: "Okay, half bits are enough" you are wrong. With 3 bits you can use 8 different values, with 8 bits 256. That means you cannot play low sounds. Okay, if you don't look at the very difficult programming the CPC is not as good as his colleagues. But the meagre printer port allows you to change that. The printer port makes it possible To build a D/A unit you normally need a special IC which costs about 15 to 20 DM and it needs an own power supply. The circuit here costs about 3 to 12 DM and does not need an own power supply. But because of this the output power is not exactly linear.You can connect the output of the circuit directly to an amplifier. All good things are three Of course, the D/A unit needs a small demo program. Because sampled instruments are very long I only have printed the file 'DATA1.BAS'. Start it and hear a little sound. Strangly it sounds much better when the upper ROM is selected. The programming The program writes directly to the hardware of the CPC. You can use the port with the adress &EFxx. Because the CPC has only a 7bit printer port (we need 8bit for the Digiblaster) we use the STROBE signal, which is inverted by the hardware, so you have to invert your sound value. Now we want to output the value &C5: LD a,&C5 ;A=&C5 |
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L'alinéa 8 de l'article L122-5 du Code de la propriété intellectuelle explique que « Lorsque l'œuvre a été divulguée, l'auteur ne peut interdire la reproduction d'une œuvre et sa représentation effectuées à des fins de conservation ou destinées à préserver les conditions de sa consultation à des fins de recherche ou détudes privées par des particuliers, dans les locaux de l'établissement et sur des terminaux dédiés par des bibliothèques accessibles au public, par des musées ou par des services d'archives, sous réserve que ceux-ci ne recherchent aucun avantage économique ou commercial ». Pas de problème donc pour nous! |
CPCrulez[Content Management System] v8.7-desktop L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko. |
