Sharp MZ-800 - Appendix B Programmable Sound Generator; (1) Description of the PSG; (2) Setting the tone frequency

Appendix B_ Programmable Sound Generator
The MZ-800 has a built-in programmable sound generator (PSG) which makes it possible to generate
3-tone chords over 6 octaves. The PSG is an SN76489AN IC.
The PSG can be controlled by sending data to I/O port address $F2.
(1) Description of the PSG
The SN76489AN IC has eight internal registers, and controls three tone generators and one noise
generator.
Block diagram
Attenuator
Attenui
060+
05
D4
03 amplitie > t
i
Output |
Tone generator 2 :
amplifier,
The internal registers required can be selected by setting bits D4 to D6 in the Ist byte of the output
data. The function of each register is shown below.
D6 | DS | D4] Function |
Frequency of tone 0
Sound volume of tone 0
Frequency of tone 1
Sound volume of tone 1
Frequency of tone 2
Sound volume of tone 2
Noise control
Noise volume
eee -ooco -r coco
Hon-cHoHo
(2) Setting the tone frequency
The tone frequency is set with the following 2-bytes of data.
! Ist by
} oe
D7|D6|D5s|D4|D3|D2|D1|DO
1 | Reg. select | Frequency 1
(lower four bits)