XR19L400 Datasheet, PDF (5/45 Pages) Exar Corporation – SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER

PRELIMINARY
XR19L400
REV. P1.0.0
SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER
1.0 PRODUCT DESCRIPTION
The XR19L400 consists of a single channel UART and RS-485 transceivers. It operates from a single +3V to
5.5V supply with data rates up to 8Mbps, while meeting all EIA/TIA-485 specifications. Its feature set is fully
compatible to the XR16V2751 device. Unlike the XR16V2751, most of the modem signals are not CMOS/TTL
level, but conform to RS-485 voltage levels. The configuration register set is 16550 UART compatible for
control, status and data transfer. Also, the L400 has 64-bytes of transmit and receive FIFOs, automatic RTS/
CTS hardware flow control, automatic Xon/Xoff and special character software flow control, transmit and
receive FIFO trigger levels, and a programmable fractional baud rate generator with a prescaler of divide by 1
or 4. Additionally, the L400 includes the ACP pin which the user can shut down the charge pump for the RS-
485 drivers. In the UART portion, the Power-Save feature isolates the databus interface to further reduce
power consumption in the Sleep mode. The L400 is fabricated using an advanced CMOS process.
Enhanced Features
The L400 UART provides a solution that supports 64 bytes of transmit and receive FIFO. Increased
performance is realized in the L400 by the transmit and receive FIFOs, FIFO trigger level controls and
automatic flow control mechanism. This allows the external processor to handle more networking tasks within
a given time. This increases the service interval giving the external CPU additional time for other applications
and reducing the overall UART interrupt servicing time. In addition, the L400 provides the ACP and Power-
Save modes that drastically reduces the power consumption when the device is not used. The combination of
the above greatly reduces the CPU’s bandwidth requirement, increases performance, and reduces power
consumption.
Intel or Motorola Data Bus Interface
The L400 provides a host interface that supports Intel or Motorola microprocessor (CPU) data bus interface.
The Intel bus compatible interface allows direct interconnect to Intel compatible type of CPUs using IOR#,
IOW# and CS# inputs for data bus operation. The Motorola bus compatible interface instead uses the R/W#
and CS# signals for data bus transactions. See pin description section for details on all the control signals. The
Intel and Motorola bus interface selection is made through the pin, I/M#.
Data Rate
The L400 is capable of operation up to 8 Mbps data rate. The device can operate either with a crystal on pins
XTAL1 and XTAL2, or external clock source on XTAL1 pin.
Internal Enhanced Register Sets
The L400 UART has a set of enhanced registers providing control and monitoring functions. Interrupt enable/
disable and status, FIFO enable/disable, selectable TX and RX FIFO trigger levels, automatic hardware/
software flow control enable/disable, programmable baud rates, modem interface controls and status, sleep
mode and infrared mode are all standard features. Following a power on reset or an external reset (and
operating in 16 or Intel Mode), the registers default to the reset condition and is compatible with the
XR16V2751.
RS-485 Interface
The L402 includes RS-485 drivers/receivers for the interface. This feature eliminates the need for an external
RS-485 transceiver. The RS-485 transceiver can be selected to operate in either the half-duplex or full-duplex
mode via the HALF/FULL# pin. The RS-485 drivers guarantee a data rate of up to 8 Mbps.
All RS-485 drivers and receivers are protected to ±15kV using the Human Body Model ground combination,
±8kV using IEC 61000-4-2 Contact Discharge, and ±15kV using IEC 61000-4-2 Air-Gap Discharge. For more
information, send an e-mail to [e-mail].
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