SCC2681T

General description

The 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 kOhm 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

Products/packages

Quality/reliability/chemical content

Quality and reliability disclaimer

Pricing/ordering/availability

Applications

Related applications
LCD TV - MMS functionality
Set-top box - MMS functionality

Block diagrams/pinning

Design support

Application Notes

AN10320; Addressing migrations of SCN devices to more advanced technologies (2004-06-29)

AN10353; Application of UART in GPS navigation system (2005-03-01)

AN10307; UART to Bluetooth interfacing (2004-08-11)

Support Documents

web; IBIS and HSPICE Model ()

Parametrics/similar products

Similar products
SCC2681T links to the similar products page containing an overview of products that are similar in function or related to the type number(s) as listed on this page. The similar products page includes products from the same catalog tree(s), relevant selection guides and products from the same functional category.

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Disclaimers

• General product disclaimer
• Quality and reliability disclaimer