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Has anybody a Casiotone 701 service manual? (Re: looking for info on casiotone 701)
2015-03-17 by cowindler01@...
I don't own a 701 (only MT-70 and 1000P) but want to document the wiring and pinout of the main ICs to search for eastereggs. Yet I only found the Casiotone 1000P service manual which has the same sound ICs but no accompaniment CPU.
I already wrote a preliminary description of the sound IC, but don't know all functions. Here is my summary:
The Music LSI "Hitachi HD43517" (42 pin DIL) is a 4 note polyphonic sound IC based on additive synthesis, that became famous by the synthesizer Casiotone 1000p. Each polyphony channel is mixing 5 harmonics (sine waves) with different digital envelopes in a similar manner like a drawbar organ. The IC outputs 12 bit digital audio to an external DAC and (like the later D933) 3 additional highest DAC bits control an expander circuit (sort of fast switching VCA, US patent 4414878) to increase dynamic range. (Without expander the DAC waveform tip looks sunken in like a collapsed copula and sounds distorted.) A sample & hold circuit then removes high frequency components. Interesting is that the IC can route its output as digital audio into another HD43517 for digital mixing through thats DAC to simplify analogue wiring. Unfortunately this wastes another DAC bit, and with only about 25kHz output frequency (due to the additional summing of 5 overtones per channel) the specs and tone quality are inferior to the earlier D931C. Interesting is that the internal signal processing (US patent 4453440) already resembles phase distortion, using phase-shifted sine wave addition from a 12 bit lookup table for fast multiplication. Frequency- and phase data resolution for each overtone is 20 bit, with 7 bit envelope controls.
Multiple HD43517 (up to 3?, existing in Casiotone 701) can be controlled by one CPU on the same 8 bit data bus. Normally each sound IC outputs audio through its own resistor ladder DAC, but in master-slave mode they can output through the DAC of the master. For this the signals DAD (serial sound data), EVD (envelope data) and SYC (sync) are sent from slave to master sound IC. (The slave's DAC has to be muted externally - e.g. by its sample & hold stage.) DAD and EVD are disconnected to select normal mode.
If you have a copy of the Casiotone 701 service manual, please scan it and inform me by e-mail. (But do not e-mail anything >300KB without warning. For large PDF use a filehoster and only e-mail a link.)
MAY THE SOFTWARE BE WITH YOU!
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