D16550
Configurable UART with FIFO
ver 2.08
internal logic is clocked with the CPU
frequency.
O V E R V I E W
The D16550 is a soft Core of a Universal
Asynchronous Receiver/Transmitter (UART)
functionally identical to the TL16C550A. The
D16550 allows serial transmission in two
modes: UART mode and FIFO mode. In FIFO
mode internal FIFOs are activated allowing 16
bytes (plus 3 bits of error data per byte in the
RCVR FIFO) to be stored in both receive and
transmit directions. D16550 performs serial-to-
parallel conversion on data characters
received from a peripheral device or a
MODEM, and parallel-to-serial conversion on
data characters received from the CPU. The
CPU can read the complete status of the
UART at any time during the functional
Two DMA modes are supported: single
transfer and multi-transfer. These modes
allow UART to interface to higher performance
DMA units, which can interleave their
transfers between CPU cycles or execute
multiple byte transfers.
The configuration capability allows user to
enable or disable during Synthesis process
the Modem Control Logic and FIFO's Control
Logic, change the FIFO size. So in
applications with area limitation and where the
UART works only in 16450 mode, disabling
Modem Control and FIFO's allow to save
about 50% of logic resources.
operation.
Status
information
reported
The D16550 has universal microcontroller
interface, allows correct communication with
D16550 no matter how D16550 clock is
related to microcontroller clock. The core is
perfect for applications, where the UART Core
and microcontroller are clocked by the same
clock signal and are implemented inside the
same ASIC or FPGA chip, as well as for
standalone implementation, where several
UARTs are required to be implemented inside
a single chip, and driven by some off-chip
devices. Thanks to universal interface D16550
core implementation and verification are very
simply, by eliminating a number of clock trees
in complete system.
includes the type and condition of the transfer
operations being performed by the UART, as
well as any error conditions (parity, overrun,
framing, or break interrupt). D16550 includes
a programmable baud rate generator that is
capable of dividing the timing reference clock
input by divisors of 1 to (216-1), and producing
a 16 × clock for driving the internal transmitter
logic. Provisions are also included to use this
16 × clock to drive the receiver logic. The
D16550 has complete MODEM control
capability, and a processor-interrupt system.
Interrupts can be programmed to the user's
requirements, minimizing the computing
required to handle the communications link.
The separate BAUD CLK line allow to set an
exact transmission speed, while the UART
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