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SCC68681 Datasheet PDF : 29 Pages
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Philips Semiconductors
Dual asynchronous receiver/transmitter (DUART)
Product data
SCC68681
DESCRIPTION
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 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 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.
FEATURES
• S68000 bus compatible
• Dual full-duplex asynchronous receiver/transmitter
• 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
• Programmable baud rate for each receiver and transmitter
selectable from:
– 22 fixed rates: 50 to 115.2 kbaud
– Non-standard rates to 115.2 kb
– Non-standard user-defined rate derived from programmable
counter/timer
– External 1× or 16× clock
• 16-bit programmable Counter/Timer
• 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 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
• Maximum data transfer rates: 1× = 1 MB/sec; 16× = 125 kB/sec
• 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
ORDERING INFORMATION
Type number
Package
Name
Description
Commercial; VCC = +5 V ± 5%; Tamb = 0 °C to +70 °C
SCC68681C1A44 PLCC44
plastic leaded chip carrier; 44 leads
SCC68681C1N40 DIP40
plastic dual in-line package; 40 leads (600 mil)
Industrial; VCC = +5 V ± 10%; Tamb = –40 °C to +85 °C
SCC68681E1A44 PLCC44
plastic leaded chip carrier; 44 leads
SCC68681E1N40 DIP40
plastic dual in-line package; 40 leads (600 mil)
2004 Apr 06
2
Version
SOT187-2
SOT129-1
SOT187-2
SOT129-1
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