Dual Asynchronous Receiver/Transmitter (DUART)
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The Philips Semiconductors SCC68681 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. It is compatible with other S68000 family devices and can also interface easily with other microprocessors. The DUART can be used in polled or interrupt driven systems. It is manufactured in a CMOS process.
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 quadruply buffered to minimize the potential of receiver overrun 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 buffer of the receiving device is full.
Also provided on the SCC68681 are a multipurpose 6-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.
製品詳細
Features
Key Features
- S68000 bus compatible
- Dual full-duplex asynchronous receiver/transmitter
- Quadruple buffered receiver data registers
- 16-bit programmable Counter/Timer
- Parity, framing and overrun error detection
- False start bit detection
- Line break detection and generation
- Multifunction programmable 16-bit counter/timer
- Maximum data transfer rates: 1× = 1 MB/s; 16× = 125 kB/s
- 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 and industrial temperature ranges available
- DIP and PLCC packages
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
Baud Rate for The Receiver and Transmitter Selectable
- 22 fixed rates: 50 to 115.2 kBd
- Non-standard rates to 115.2 kB
- Non-standard user-defined rate derived from programmable counter/timer
- External 1x or 16x clock
Programmable Channel Mode
- Normal (full-duplex)
- Automatic echo
- Local loopback
- Remote loopback
Multi-function 6-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
- Interrupt vector output on interrupt acknowledge
- Output port can be configured to provide a total of up to six separate wire-ORable interrupt outputs