Intel® Arria® 10 Hard Processor System Technical Reference Manual

ID 683711
Date 8/28/2023
Public
Document Table of Contents

22.4.1. FIFO Buffer Support

The UART controller includes 128-byte FIFO buffers to buffer transmit and receive data. FIFO buffer access mode allows the master to write the receive FIFO buffer and to read the transmit FIFO buffer for test purposes. FIFO buffer access mode is enabled with the FIFO access register (FAR). Once enabled, the control portions of the transmit and receive FIFO buffers are reset and the FIFO buffers are treated as empty. †

When FIFO buffer access mode is enabled, you can write data to the transmit FIFO buffer as normal; however, no serial transmission occurs in this mode and no data leaves the FIFO buffer. You can read back the data that is written to the transmit FIFO buffer with the transmit FIFO read (TFR) register. The TFR register provides the current data at the top of the transmit FIFO buffer. †

Similarly, you can also read data from the receive FIFO buffer in FIFO buffer access mode. Since the normal operation of the UART is halted in this mode, you must write data to the receive FIFO buffer to read it back. The receive FIFO write (RFW) register writes data to the receive FIFO buffer. The upper two bits of the 10-bit register write framing errors and parity error detection information to the receive FIFO buffer. Bit 9 of RFW indicates a framing error and bit 8 of RFW indicates a parity error. Although you cannot read these bits back from the receive buffer register, you can check the bits by reading the line status register (LSR), and by checking the corresponding bits when the data in question is at the top of the receive FIFO buffer. †