This is meant as a parallel port sound card like a Covox Speech Thing. Instead of R-2R resistors, the chip will generate the analog audio output using PWM and First-order sigma-delta modulator.
No particular test required.
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | Bit 0 of Parallel port (LSB) | Standard PWM audio output | Direct from input 0 |
| 1 | Bit 1 of Parallel port | Sigma-delta modulator output | Direct from input 1 |
| 2 | Bit 2 of Parallel port | From ena pin | Direct from input 2 |
| 3 | Bit 3 of Parallel port | From clk pin | Direct from input 3 |
| 4 | Bit 4 of Parallel port | From rst_n pin | Direct from input 4 |
| 5 | Bit 5 of Parallel port | Static 1 | Direct from input 5 |
| 6 | Bit 6 of Parallel port | Static 0 | Direct from input 6 |
| 7 | Bit 7 of Parallel port (MSB) | Static 1 | Direct from input 7 |