YM2149

The YM2149 is a software-controlled sound generator (SSG).The SSG (Software-Controlled Sound Generator) is an NMOS-LSI device designed to be capable of music generation. It only requires the microprocessor or microcomputer (CPU) to initialize its register array, thus reducing the load on the CPU. Music generation is carried out by the three sequence square wave generator, noise generator, and envelope generator according to the set parameters. This allows for the generation of music, special effects,warnings, and various other types of sounds.

Features of the YM2149 are:(1)5V single power supply; (2)easy connection to 8 bit or 16 bit CPU; (3)simple connection to external system through 2 sequence 8 bit I/O port; (4)wide voicing range of 8 octaves; (5)smooth attenuation by 5 bit envelope generator; (6)built-in 5 bit D/A convertor; (7)input of double frequency clock can be handled by built-in clock frequency divider; (8)TTL compatible level; (9)low power consumption (typical 125mW); (10)40 pin plastic DIL package; (11)pin compatible with AY-3-8910 manuafactured by GI.

The absolute maximum ratings of the YM2149 can be summarized as:(1)pin voltage:-0.3 to 7.0 V;(2)storage temperature:-50 to +125;(3)operating ambient temperature:0 to +70.The frequencies of the square wave generated by the music generators for the three channels(A, B, and C) are controlled by registers Ro through R5. R0 and R1 control channel A, R2 and R3 are used for channel B, and R4 and R5 control channel C. The oscillation frequency fT is obtained in the following manner from value of the register TP (decimal).When SEL is driven to the high level, the input clock is taken voltage level of SEL is low, the input clock is divided by 2 to as the master clock. When the obtain the master clock. This pin has pullup resistance, allowing for full pin compatibility with the AY-3-8910 manufactured by AI, when this pin is not connected to anything.