The Uart Master receives characters from UART and performs read / writes on a bus accordingly. The purpose is to get easy access to the data bus via uart for development.
The UartMaster has two registers: The address register and the data register.
If the UartMaster receives (case sensitive!)
- a 'L' character, the address register is selected
- a 'W' character, the data register is selected
- lower case hex character (0-9,a-f), it will write the nibble it to the selected register, and then advances to the next nibble of that register.
- a 'R' character is received, it reads 8-bit of data from the configured address, converts it to a "two-nibbled hex-string", like "6d" and sends it over the Uart.
The address register is 16-bit wide. If it has been selected, the first write goes to the highest nibble of the register (addr[15:12]), the next write goes into addr[11:8], and so on.
The data register is 8-bit wide, the higher nibble is also written first. If two nibbles have been written to the register, the data is written onto the bus with the configured address.
Each read / write does an auto-increment of the address register.