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SCN2681T Datasheet(PDF) 2 Page - NXP Semiconductors

Part No. SCN2681T
Description  Dual asynchronous receiver/transmitter DUART
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Maker  PHILIPS [NXP Semiconductors]
Homepage  http://www.nxp.com

SCN2681T Datasheet(HTML) 2 Page - NXP Semiconductors

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Philips Semiconductors
Product specification
Dual asynchronous receiver/transmitter (DUART)
1998 Sep 04
853–1002 19970
The Philips Semiconductors SCN2681 Dual Universal
Asynchronous Receiver/Transmitter (DUART) is a single-chip
MOS-LSI communications device that provides two independent
full-duplex asynchronous receiver/transmitter channels in a single
package. The SCN2681T features a faster bus cycle time than the
standard SCN2681. The quick bus cycle eliminates or reduces the
need for wait states with fast CPUs and permits high throughput in
I/O intensive systems. Higher external clock rates may be used with
the transmitter, receiver and counter timer which in turn provide
greater versatility in baud rate generation. The SCN2681T
interfaces directly with microprocessors and may be used in a polled
or interrupt driven system.
The operating mode and data format of each channel can be
programmed independently. Additionally, each receiver and
transmitter can select its operating speed as one of eighteen fixed
baud rates, a 16X clock derived from a programmable counter/timer,
or an external 1X or 16X clock. The baud rate generator and
counter/timer can operate directly from a crystal or from external
clock inputs. The ability to independently program the operating
speed of the receiver and transmitter make the DUART particularly
attractive for dual-speed channel applications such as clustered
terminal systems.
Each receiver is quadruple buffered to minimize the potential of
receiver over-run or to reduce interrupt overhead in interrupt driven
systems. In addition, a flow control capability is provided to disable
a remote DUART transmitter when the receiver buffer is full.
Also provided on the SCN2681T are a multipurpose 7-bit input port
and a multipurpose 8-bit output port. These can be used as general
purpose I/O ports or can be assigned specific functions (such as
clock inputs or status/interrupt outputs) under program control.
For a complete functional description and programming information
for the SCN2681T, refer to the SCN2681 product specification.
Fast bus cycle times reduce or eliminate CPU wait states
Dual full-duplex asynchronous receiver/transmitters
Quadruple buffered receiver data registers
Programmable data format
– 5 to 8 data bits plus parity
– Odd, even, no parity or force parity
– 1, 1.5 or 2 stop bits programmable in 1/16-bit increments
16-bit programmable Counter/Timer
Programmable baud rate for each receiver and transmitter
selectable from:
– 22 fixed rates: 50 to 115.2k baud
– Non-standard rates to 115.2
– Non-standard user-defined rate derived from programmable
– External 1X or 16X clock
Parity, framing, and overrun error detection
False start bit detection
Line break detection and generation
Programmable channel mode
– Normal (full-duplex)
– Automatic echo
– Local loopback
– Remote loopback
Multi-function programmable 16-bit counter/timer
Multi-function 7-bit input port
– Can serve as clock or control inputs
– Change of state detection on four inputs
– 100k
Ω typical pull-up resistors
Multi-function 8-bit output port
– Individual bit set/reset capability
– Outputs can be programmed to be status/interrupt signals
Versatile interrupt system
– Single interrupt output with eight maskable interrupting
– Output port can be configured to provide a total of up to six
separate wire-ORable interrupt outputs
Maximum data transfer rates:
1X – 1MB/sec transmitter and receiver; 16X – 500kB/sec receiver
and 250kB/sec transmitter
Automatic wake-up mode for multidrop applications
Start-end break interrupt/status
Detects break which originates in the middle of a character
On-chip crystal oscillator
Single +5V power supply
Commercial and industrial temperature ranges available
VCC = +5V +10%, TA = 0°C to +70°C
40-Pin Plastic Dual In-Line Package (600mil-wide DIP)
44-Pin Plastic Lead Chip Carrier (PLCC)
NOTE: For a full register description and programming information see the SCN2681.

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