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SCC2681TC1A44
Dual asynchronous receiver/transmitter (DUART)
Product data 2004 Apr 06
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
DESCRIPTIONThe Philips Semiconductors SCC2681 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 SCC2681T features a faster bus cycle time than the
standard SCC2681. 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 SCC2681T interfaces
directly with microprocessors and may be used in a polled or
interrupt driven system. It is manufactured in CMOS technology.
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 16× clock derived from a programmable counter/timer,
or an external 1× or 16× 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 SCC2681T 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 SCC2681T, refer to the SCC2681 product specification.
FEATURES 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 115.2 k baud
Non-standard rates to 115.2
Non-standard user-defined rate derived from programmable
counter/timer
External 1× or 16× 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
100 kΩ typical pull-up resistors Multi-function 8-bit output port
Individual bit set/reset capability
Outputs can be programmed to be status/interrupt/DMA signals
Auto 485 turn-around Versatile interrupt system
Single interrupt output with eight maskable interrupting
conditions
Output port can be configured to provide a total of up to six
separate wire-ORable interrupt outputs Maximum data transfer rates:
1× – 1 MB/sec transmitter and receiver
16× – 500 kB/sec receiver and 250 kB/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 +5 V power supply Commercial temperature range
ORDERING INFORMATION
NOTE: For a full register description and programming information see the SCC2681.
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
BLOCK DIAGRAM
Figure 1. Block Diagram
NOTE:Refer to SCC2681 for functional description.
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
PIN CONFIGURATION
Figure 2. Pin configuration
PIN DESCRIPTION
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
ABSOLUTE MAXIMUM RATINGS1
NOTES: Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and
functional operation of the device at these or any other conditions above those indicated in the operation section of this specification is not
implied. For operating at elevated temperatures, the device must be derated based on +150 °C maximum junction temperature. This product includes circuitry specifically designed for the protection of its internal devices from damaging effects of excessive static
charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying any voltages larger than the rated maxima.
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
DC ELECTRICAL CHARACTERISTICS1, 2, 3 Tamb = 0 °C to +70 °C; VCC = +5.0 V ± 10%
NOTES: Parameters are valid over specified temperature range. All voltage measurements are referenced to ground (GND). For testing, all inputs swing between 0.4 V and 2.4 V with a transition time of
5 ns maximum. For X1/CLK this swing is between 0.4 V and 4.4 V. All time measurements are referenced at input voltages of 0.8 V and
2.0 V and output voltages of 0.8 V and 2.0 V, as appropriate. Typical values are at +25 °C, typical supply voltages, and typical processing parameters. Test conditions for outputs: CL = 150 pF, except interrupt outputs. Test conditions for interrupt outputs: CL = 50 pF, RL = 2.7 kΩ to VCC. All outputs are disconnected. Inputs are switching between CMOS levels of VCC – 0.2 V and VSS + 0.2 V.
Philips Semiconductors Product data
SCC2681TDual asynchronous receiver/transmitter (DUART)
AC ELECTRICAL CHARACTERISTICS1, 2, 3, 4
NOTES: Parameters are valid over specified temperature range. See Ordering information table for applicable operating temperature range and VCC
supply range.
