XR16M2751
1.62V TO 3.63V HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
AUGUST 2007
REV. 1.0.0
GENERAL DESCRIPTION
The XR16M2751
1
(M2751) is a high performance
dual universal asynchronous receiver and transmitter
(UART) with 64 byte TX and RX FIFOs. The device
operates from 1.62 to 3.63 volts and is pin-to-pin and
software compatible to Exar’s XR16V2751. The
device includes 2 additional capabilities over the
XR16M2750: Intel and Motorola data bus selection
and a “PowerSave” mode to further reduce sleep
current to a minimum during sleep mode. It supports
the Exar’s enhanced features of programmable FIFO
trigger level and FIFO level counters, automatic
hardware (RTS/CTS) and software flow control,
automatic RS-485 half duplex direction control output
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 8 Mbps at 3.3 Volt and 8X sampling
clock. The M2751 is available in a 48-pin TQFP
package.
N
OTE
:
1 Covered by U.S. Patent #5,649,122 and #5,949,787
FEATURES
•
1.62 to 3.63 Volt Operation
•
Pin-to-pin compatible to Exar’s XR16V2751 in the
48-TQFP package
•
Two independent UART channels
■
■
■
■
■
■
■
■
■
■
■
Data rate of up to 8 Mbps at 3.3 V
Data rate of up to 6.25 Mbps at 2.5 V
Data rate of up to 4 Mbps at 1.8 V
Fractional Baud Rate Generator
Transmit and Receive FIFOs of 64 bytes
Programmable TX and RX FIFO Trigger Levels
Transmit and Receive FIFO Level Counters
Automatic Hardware (RTS/CTS) Flow Control
Selectable Auto RTS Flow Control Hysteresis
Automatic Software (Xon/Xoff) Flow Control
Automatic RS-485 Half-duplex
Control Output via RTS#
Direction
■
■
■
Wireless Infrared (IrDA 1.0) Encoder/Decoder
Automatic sleep mode with wake-up interrupt
Full modem interface
APPLICATIONS
•
Portable Appliances
•
Telecommunication Network Routers
•
Ethernet Network Routers
•
Cellular Data Devices
•
Factory Automation and Process Controls
F
IGURE
1. XR16M2751 B
LOCK
D
IAGRAM
•
PowerSave Feature reduces sleep current to 15 µA
•
Device Identification and Revision
•
Crystal oscillator (up to 24MHz) or external clock
(up to 64MHz) input
•
48-TQFP package
PwrSave
A2:A0
D7:D0
IOR# (VCC)
IOW# (R/W#)
CSA# (CS#)
CSB# (A3)
INTA (IRQ#)
INTB (logic 0)
TXRDYA#
TXRDYB#
RXRDYA#
RXRDYB#
Reset (Reset#)
16/68#
CLKSEL
HDCNTL#
Intel or
Motorola
Data Bus
Interface
UART Channel A
UART
Regs
BRG
64 Byte TX FIFO
TX & RX
IR
ENDEC
1.62 to 3.6V VCC
GND
TXA, RXA, DTRA#,
DSRA#, RTSA#,
DTSA#, CDA#, RIA#,
OP2A#
64 Byte RX FIFO
TXB, RXB, DTRB#,
DSRB#, RTSB#,
CTSB#, CDB#, RIB#,
OP2B#
XTAL1
XTAL2
UART Channel B
(same as Channel A)
Crystal Osc/Buffer
Exar
Corporation 48720 Kato Road, Fremont CA, 94538
•
(510) 668-7000
•
FAX (510) 668-7017
•
www.exar.com
XR16M2751
1.62V TO 3.63V HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
F
IGURE
2. P
IN
O
UT
A
SSIGNMENT
REV. 1.0.0
43 TXRDYA#
47 D3
46 D2
44 D0
39
37 HDCNTL#
DSRA#
38 CTSA#
41 RIA#
42 VCC
48 D4
45 D1
40 CDA#
D5
D6
D7
RXB
RXA
TXRDYB#
TXA
TXB
OP2B#
CSA#
CSB#
PWRSAVE
1
2
3
4
5
6
7
8
9
10
11
12
IOW# 15
XTAL1 13
CDB# 16
RXRDYB# 18
IOR# 19
20
RIB# 21
RTSB# 22
CTSB# 23
XTAL2 14
GND 17
16/68#
24
36 RESET
35 DTRB#
34 DTRA#
33 RTSA#
32 OP2A#
XR16M2751
48-pin TQFP
in 16 (Intel) Mode
31 RXRDYA#
30 INTA
29 INTB
28 A0
27 A1
43 TXRDYA#
37 HDCNTL#
26 A2
25 CLKSEL
48 D4
47 D3
46 D2
45 D1
44 D0
DSRA#
39
DSRB#
38 CTSA#
41 RIA#
42 VCC
40 CDA#
D5
VCC
D6
D7
RXB
RXA
TXRDYB#
TXA
TXB
OP2B#
CS#
A3
PWRSAVE
1
2
3
4
5
6
7
8
9
10
11
12
R/W# 15
XTAL1 13
RXRDYB# 18
NC 19
20
RTSB# 22
CTSB# 23
CDB# 16
XTAL2 14
RIB# 21
GND 17
16/68#
24
36 RESET#
35 DTRB#
34 DTRA#
33 RTSA#
32 OP2A#
XR16M2751
48-pin TQFP
in 68 (Motorola) Mode
31 RXRDYA#
30 IRQ#
29 NC
28 A0
27 A1
26 A2
25 CLKSEL
DSRB#
GND
ORDERING INFORMATION
P
ART
N
UMBER
XR16M2751IM48
P
ACKAGE
48-Lead TQFP
O
PERATING
T
EMPERATURE
R
ANGE
-40°C to +85°C
D
EVICE
S
TATUS
Active
2
XR16M2751
REV. 1.0.0
1.62V TO 3.63V HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
PIN DESCRIPTIONS
Pin Description
N
AME
48-TQFP
P
IN
#
T
YPE
D
ESCRIPTION
DATA BUS INTERFACE
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
IOR#
(VCC)
26
27
28
3
2
1
48
47
46
45
44
19
I
Address data lines [2:0]. These 3 address lines select one of the internal registers in
UART channel A/B during a data bus transaction.
Data bus lines [7:0] (bidirectional).
I/O
I
When 16/68# pin is HIGH, the Intel bus interface is selected and this input becomes
read strobe (active low). The falling edge instigates an internal read cycle and
retrieves the data byte from an internal register pointed by the address lines [A2:A0],
puts the data byte on the data bus to allow the host processor to read it on the rising
edge.
When 16/68# pin is LOW, the Motorola bus interface is selected and this input is not
used and should be connected to VCC.
When 16/68# pin is HIGH, it selects Intel bus interface and this input becomes write
strobe (active low). The falling edge instigates the internal write cycle and the rising
edge transfers the data byte on the data bus to an internal register pointed by the
address lines.
When 16/68# pin is LOW, the Motorola bus interface is selected and this input
becomes read (HIGH) and write (LOW) signal.
When 16/68# pin is HIGH, this input is chip select A (active low) to enable channel A
in the device.
When 16/68# pin is LOW, this input becomes the chip select (active low) for the
Motorola bus interface.
When 16/68# pin is HIGH, this input is chip select B (active low) to enable channel B
in the device.
When 16/68# pin is LOW, this input becomes address line A3 which is used for chan-
nel selection in the Motorola bus interface. Input logic 0 selects channel A and logic 1
selects channel B.
When 16/68# pin is HIGH for Intel bus interface, this output becomes channel A inter-
rupt output. The output state is defined by the user through the software setting of
MCR[3]. INTA is set to the active mode and OP2A# output to a logic 0 when MCR[3]
is set to a logic 1. INTA is set to the three state mode and OP2A# to a logic 1 when
MCR[3] is set to a logic 0. See MCR[3].
When 16/68# pin is LOW for Motorola bus interface, this output becomes device
interrupt output (active low, open drain). An external pull-up resistor is required for
proper operation.
IOW#
(R/W#)
15
I
CSA#
(CS#)
10
I
CSB#
(A3)
11
I
INTA
(IRQ#)
30
O
3
XR16M2751
1.62V TO 3.63V HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
Pin Description
N
AME
INTB
48-TQFP
P
IN
#
29
T
YPE
O
D
ESCRIPTION
UART channel B Interrupt output. The output state is defined by the user through the
software setting of MCR[3]. INTB is set to the active mode and OP2B# output LOW
when MCR[3] is set to a logic 1. INTB is set to the three state mode and OP2B# out-
put HIGH when MCR[3] is set to a logic 0 (default). See MCR[3].
UART channel A Transmitter Ready (active low). The output provides the TX FIFO/
THR status for transmit channel A. See
Table 3
. If it is not used, leave it uncon-
nected.
UART channel A Receiver Ready (active low). This output provides the RX FIFO/
RHR status for receive channel A. See
Table 3
. If it is not used, leave it uncon-
nected.
UART channel B Transmitter Ready (active low). The output provides the TX FIFO/
THR status for transmit channel B. See
Table 4
. If it is not used, leave it uncon-
nected.
UART channel B Receiver Ready (active low). This output provides the RX FIFO/
RHR status for receive channel B. See
Table 3
. If it is not used, leave it uncon-
nected.
REV. 1.0.0
TXRDYA#
43
O
RXRDYA#
31
O
TXRDYB#
6
O
RXRDYB#
18
O
MODEM OR SERIAL I/O INTERFACE
TXA
7
O
UART channel A Transmit Data or infrared encoder data. Standard transmit and
receive interface is enabled when MCR[6] = 0. In this mode, the TX signal will be
HIGH during reset or idle (no data). Infrared IrDA transmit and receive interface is
enabled when MCR[6] = 1. In the Infrared mode, the inactive state (no data) for the
Infrared encoder/decoder interface is LOW. If it is not used, leave it unconnected.
UART channel A Receive Data or infrared receive data. Normal receive data input
must idle HIGH. The infrared receiver pulses typically idles at LOW but can be
inverted by software control prior going in to the decoder, see MCR[6] and FCTR[2].
If this pin is not used, tie it to VCC or pull it high via a 100k ohm resistor.
UART channel A Request-to-Send (active low) or general purpose output. This out-
put must be asserted prior to using auto RTS flow control, see EFR[6], MCR[1],
FCTR[1:0], EMSR[5:4] and IER[6]. For auto RS485 half-duplex direction control, see
FCTR[3] and EMSR[3].
UART channel A Clear-to-Send (active low) or general purpose input. It can be
used for auto CTS flow control, see EFR[7], and IER[7]. This input should be con-
nected to VCC when not used.
UART channel A Data-Terminal-Ready (active low) or general purpose output. If it is
not used, leave it unconnected.
UART channel A Data-Set-Ready (active low) or general purpose input. This input
should be connected to VCC when not used. This input has no effect on the UART.
UART channel A Carrier-Detect (active low) or general purpose input. This input
should be connected to VCC when not used. This input has no effect on the UART.
UART channel A Ring-Indicator (active low) or general purpose input. This input
should be connected to VCC when not used. This input has no effect on the UART.
RXA
5
I
RTSA#
33
O
CTSA#
38
I
DTRA#
DSRA#
CDA#
RIA#
34
39
40
41
O
I
I
I
4
XR16M2751
REV. 1.0.0
1.62V TO 3.63V HIGH PERFORMANCE DUART WITH 64-BYTE FIFO
Pin Description
N
AME
OP2A#
48-TQFP
P
IN
#
32
T
YPE
O
D
ESCRIPTION
Output Port 2 Channel A - The output state is defined by the user and through the
software setting of MCR[3]. INTA is set to the active mode and OP2A# output LOW
when MCR[3] is set to a logic 1. INTA is set to the three state mode and OP2A# out-
put HIGH when MCR[3] is set to a logic 0. See MCR[3]. If INTA is used, this output
should not be used as a general output else it will disturb the INTA output functional-
ity.
UART channel B Transmit Data or infrared encoder data. Standard transmit and
receive interface is enabled when MCR[6] = 0. In this mode, the TX signal will be
HIGH during reset or idle (no data). Infrared IrDA transmit and receive interface is
enabled when MCR[6] = 1. In the Infrared mode, the inactive state (no data) for the
Infrared encoder/decoder interface is LOW. If it is not used, leave it unconnected.
UART channel B Receive Data or infrared receive data. Normal receive data input
must idle HIGH. The infrared receiver pulses typically idles at logic 0 but can be
inverted by software control prior going in to the decoder, see MCR[6] and FCTR[2].
If this pin is not used, tie it to VCC or pull it high via a 100k ohm resistor.
UART channel B Request-to-Send (active low) or general purpose output. This port
must be asserted prior to using auto RTS flow control, see EFR[6], MCR[1],
FCTR[1:0], EMSR[5:4] and IER[6]. For auto RS485 half-duplex direction control, see
FCTR[3] and EMSR[3].
UART channel B Clear-to-Send (active low) or general purpose input. It can be
used for auto CTS flow control, see EFR[7], and IER[7]. This input should be con-
nected to VCC when not used.
UART channel B Data-Terminal-Ready (active low) or general purpose output. If it is
not used, leave it unconnected.
UART channel B Data-Set-Ready (active low) or general purpose input. This input
should be connected to VCC when not used. This input has no effect on the UART.
UART channel B Carrier-Detect (active low) or general purpose input. This input
should be connected to VCC when not used. This input has no effect on the UART.
UART channel B Ring-Indicator (active low) or general purpose input. This input
should be connected to VCC when not used. This input has no effect on the UART.
Output Port 2 Channel B - The output state is defined by the user and through the
software setting of MCR[3]. INTB is set to the active mode and OP2B# output LOW
when MCR[3] is set to a logic 1. INTB is set to the three state mode and OP2B# out-
put HIGH when MCR[3] is set to a logic 0. See MCR[3]. If INTB is used, this output
should not be used as a general output else it will disturb the INTB output functional-
ity.
TXB
8
O
RXB
4
I
RTSB#
22
O
CTSB#
23
I
DTRB#
DSRB#
CDB#
RIB#
OP2B#
35
20
16
21
9
O
I
I
I
O
ANCILLARY SIGNALS
XTAL1
XTAL2
PwrSave
13
14
12
I
O
I
Crystal or external clock input.
Crystal or buffered clock output.
PowerSave (active high). This feature isolates the 2751’s data bus interface from the
host preventing other bus activities that cause higher power drain during sleep mode.
See Sleep Mode with Auto Wake-up and PowerSave Feature section for details.
5
