4 bits should be loaded into registers through the data pins twice - once for the LSB of a byte, once for the MSB of a byte (specified using the mode pins).
Once ready, mode can be set to transmit to send the loaded byte over UART.
When mode[1,2]=01, data is clocked in as the least-significant 4-bits for a UART transmissions. When mode[1,2]=10, the same occurs for the most-significant 4-bits. When mode[1,2]=11, the complete data should get sent over UART.
Arduino can be used for testing UART RX
| # | Input | Output |
|---|---|---|
| 0 | clock | uart_tx |
| 1 | reset | |
| 2 | data1 | |
| 3 | data2 | |
| 4 | data3 | |
| 5 | data4 | |
| 6 | mode1 | |
| 7 | mode2 |