Tiny Tapeout > Tiny Tapeout Chips > Tiny Tapeout SKY 26a > 871 IEEE Open Silicon 2026: UTB UART Transmitter basic
871 IEEE Open Silicon 2026: UTB UART Transmitter basic
871 : IEEE Open Silicon 2026: UTB UART Transmitter basic
- Author: George Archbold and Semillero SIMIC UTB
- Description: An 8-bit serial transmitter that converts parallel ASCII data (supporting characters from 0x40 to 0x5F) into a standard UART frame using a shift register architecture
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- Clock: 0 Hz
How it works
The circuit utilizes a chain of D Flip-Flops (flop1 through flop18) and Multiplexers to form a large Parallel-In-Serial-Out (PISO) shift register. When the control switch is set to "Load," the input ASCII bits are captured into the register chain. Once switched to "Transmit," the data is shifted serially bit-by-bit through the uo_out[7] pin, automatically including the necessary start, stop, and idle bits to form a valid UART frame.
How to test
- Set the desired ASCII value (between 0x40 and 0x5F) using the input DIP switches.
- Toggle the Load switch (ui_in[6]) and pulse the clock to capture the data into the registers.
- Set the switch to TX mode to begin the serial transmission.
- Monitor the serial output on pin uo_out[7] and observe the status LEDs to verify the sequence.
External hardware
- 8-position DIP switch for data and mode selection.
- Common cathode 7-segment display for debugging.
- Status LEDs to monitor the bit shifting process.
- A logic analyzer or UART-to-USB converter to verify the serial signal on a PC.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | tx_check | ||
| 1 | bit0 | ||
| 2 | bit1 | ||
| 3 | bit2 | ||
| 4 | bit3 | ||
| 5 | bit4 | out_enable | |
| 6 | loadTX | ||
| 7 | out_en | TX |