UART

The UART a single register at address $900. It uses a fixed serial configuration of 115200 bps, 8 data bits, 1 stop bit, no parity.

Reading the UART register

bit	31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16
Value	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-

bit	15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00
Value	-	-	-	-	-	-	A	B	d	d	d	d	d	d	d	d

Bitfields	Description
A	data available, at least one byte has been received
B	TX busy, a byte is being transmitted and no data can be written
d	8 data bits

bit	31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16
Value	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-

bit	15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00
Value	-	-	-	-	-	T	C	-	d	d	d	d	d	d	d	d

Bitfields	Description
T	transmit enable, writes a data byte
C	clear receiver, acknowledges a received byte
d	8 data bits

A 16 byte FIFO is used when receiving data.

When reading data, each byte needs to be acknowledged by writing the C flag to the UART register.

When the FIFO is empty, the A flag in the UART register will be 0.