Artesyn iVPX7225 Installation and Use (April 2015) - Manual (Page 148)

FPGA Registers
iVPX7225 Installation and Use (6806800S11C) 129
7.3.1.1 Received Buffer Register (RBR)
In non-FIFO mode, this register holds the character received by the UART's Receive Shift
Register. If fewer than eight bits are received, the bits are right-justified and the leading bits are
zeroed. Reading the register empties the register and resets the Data Ready (DR) bit in the Line
Status Register to zero. Other (error) bits in the Line Status Register are not cleared. In FIFO
mode, this register latches the value of the data byte at the top of the FIFO.
7.3.1.2 Transmitter Holding Register (THR)
This register holds the next data byte to be transmitted. When the Transmit Shift Register
becomes empty, the contents of the Transmit Holding Register are loaded into the shift
register and the transmit data request (TDRQ) bit in the Line Status Register is set to one.
In FIFO mode, writing to THR puts data to the top of the FIFO. The data at the bottom of the
FIFO is loaded to the shift register when it is empty.
Table 7-44 Receiver Buffer Register (RBR) if DLAB=0
IO Address: Base
Bit # Description Default Access
7:0 Receiver Buffer register (RBR) Undef. R
Table 7-45 Transmitter Holding Register (THR) if DLAB=0
IO Address: Base
Bit # Description Default Access
7:0 Transmitter Holding Register (THR) Undef. W