Changes
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=== Tone Generator Control (Registers R0,R1,R2,R3,R4,R5) ===
The frequency of each square wave generated by the three Tone Generators (one each for Channels A,B and C) is obtained in the PSG by first counting down the input clock by 16, then by furthur counting down the result by the programmed 12-bit Tone Period value. Each 12-bit value is obtained in the PSG by combining the contents of the relative Course and Fine Tune registers, as illustrated in the following:
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=== Noise Generator Control (Register R6)===
The frequency of the noise source is obtained in the PSG by first counting down the input clock by 16, then by furthur counting down the result by the programmed 5-bit Noise Period value. This 5-bit value consists of the lower 5-bits (B4--B0) of register R6, as illustrated in the following:
NOT USED 5-bit Noise Period (NP) to Noise Generator
=== Mixer Control Enable (Register R7)===
Register R7 is multi-function /Enable register which controls the three Noise/Tone Mixers and the two general purpose I/O Ports.
B A C B A C B A
=== Amplitude Control (Registers R10,R11,R12) ===
The amplitudes of the signals generated by each of the three D/A Converters (one each for Channels A,B and C) is determined by the contents of the lower 5-bits (B4--B0) of registers R10,R11 and R12 as illustrated in the following:
=== Envelope Generator Control (Registers R13,R14 and R15) ===
To acomplish the generation of fairly complex envelope patterns, two independant methods of control are provided in the PSG: first, it is possible to vary the frequency of the envelope using registers R13 and R14; and second, the relative shape and cycle pattern of the envelope can be varied using register R15. The following paragraphis explain the details of the envelope control functions, describing first the envelope period control and then the envelope shape/cycle control.
