
Exar Corporation 48720 Kato Road, Fremont CA, 94538 (510) 668-7000 FAX (510) 668-7017 www.exar.com
XR16M2651
HIGH PERFORMANCE DUART WITH 32-BYTE FIFO AND POWERSAVE FEATURE
MAY 2007
REV. 1.0.2
GENERAL DESCRIPTION
The XR16M26511 (M2651) is a high performance
dual universal asynchronous receiver and transmitter
(UART) with 32 byte TX and RX FIFOs. The device
operates from 1.62 to 3.63 volts and is pin-to-pin and
software
compatible
to
the
XR16V2551
and
XR16L2551. The device includes 2 additional
capabilities over the XR16M2650: Intel and Motorola
data bus selection and a “PowerSave” mode to
minimize the sleep current. It supports Exar’s
enhanced features of selectable FIFO trigger level,
automatic hardware (RTS/CTS) and software flow
control, and a complete modem interface. An internal
loopback capability allows system diagnostics.
Independent programmable fractional baud rate
generators are provided in each channel to select
data rates up to 16 Mbps at 3.3 Volt with 4X sampling
clock. The M2651 is available in 48-pin TQFP and 32-
pin QFN packages.
NOTE: 1 Covered by U.S. Patent #5,649,122
APPLICATIONS
Portable Appliances
Telecommunication Network Routers
Ethernet Network Routers
Cellular Data Devices
Factory Automation and Process Controls
FEATURES
1.62 to 3.63 Volt Operation
Pin-to-pin and software compatible to Exar’s
XR16L2551, XR16V2551 and XR16M2551
Two independent UART channels
■ Register set is 16550 compatible
■ Data rate of up to 16 Mbps at 3.3 V
■ Data rate of up to 12.5 Mbps at 2.5 V
■ Data rate of up to 8 Mbps at 1.8V
■ Fractional Baud Rate Generator
■ Transmit and Receive FIFOs of 32 bytes
■ Selectable TX and RX FIFO Trigger Levels
■ Automatic Hardware (RTS/CTS) Flow Control
■ Automatic Software (Xon/Xoff) Flow Control
■ Wireless Infrared (IrDA 1.0) Encoder/Decoder
■ Automatic sleep mode with wake-up interrupt
■ Full modem interface
PowerSave Feature reduces sleep current to 15 A
Device Identification and Revision
Crystal oscillator (up to 24MHz) or external clock
(up to 64MHz) input
48-TQFP and 32-QFN packages
FIGURE 1. XR16M2651 BLOCK DIAGRAM
XTAL1
XTAL2
Crystal Osc/Buffer
TXA, RXA, DTRA#,
DSRA#, RTSA#,
CTSA#, CDA#, RIA#,
OP2A#
Intel or
Motorola
Data Bus
Interface
UART Channel A
32 Byte TX FIFO
32 Byte RX FIFO
BRG
IR
ENDEC
TX & RX
UART
Regs
1.62 to 3.63V VCC
GND
TXB, RXB, DTRB#,
DSRB#, RTSB#,
CTSB#, CDB#, RIB#,
OP2B#
UART Channel B
(same as Channel A)
A2:A0
D7:D0
CSA# (CS#)
16/68#
CSB# (A3)
INTA (IRQ#)
INTB (logic 0)
PwrSave
IOW# (R/W#)
IOR# (VCC)
Reset (Reset#)
CLKSEL
TXRDYA#
TXRDYB#
RXRDYA#
RXRDYB#