677 TwoChannelSquareWaveGenerator
677 : TwoChannelSquareWaveGenerator
- Author: Sam Kho
- Description: Like having two apple2-style speakers
- GitHub repository
- Clock: 256000 Hz
How it works
Two 8-bit inputs, TA and TB, are used to reload internal countdown timers when they reach zero, at which time, respective outputs OUTA and OUTB are toggled. A 2-bit SUM output is also provided as a convenience (SUM = OUTA + OUTB).
How to test
Apply arbitrary 8-bit reload values to TA (ui_in) and TB (uio_in). Probe OUTA and OUTB with oscilloscope or logic analyzer. Time period for outputs is proportional to (input+1); i.e. to get two waves with period T and period 2T, provide values like 3 and 7 (instead of 4 and 8). Also check 2-bit output SUM (should be OUTA + OUTB, possibly delayed by one cycle).
External hardware
External hardware not needed, but intent is to drive speakers (probably bring down voltage level via resistor dividers, then feed into speaker amplifier).
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | TA0 | OUTA | TB0 |
| 1 | TA1 | OUTB | TB1 |
| 2 | TA2 | SUM0 | TB2 |
| 3 | TA3 | SUM1 | TB3 |
| 4 | TA4 | TB4 | |
| 5 | TA5 | TB5 | |
| 6 | TA6 | TB6 | |
| 7 | TA7 | TB7 |