Dual Asynchronous Communications
Interface Adapter (DACIA)
The Rockwell CMOS R68C552 Dual Asynchronous Communica-
tions Interface Adapter (DACIA) provides an easily implemented,
program controlled two-channel interface between 16-bit
microprocessor-based systems and serial communication data
sets and modems.
The DACIA is designed for maximum programmed control from
the microprocessor (MPU) to simplify hardware implementation.
Dual sets of registers allow independent control and monitoring
of each channel. (
Transmitter and Receiver bit rates may be controlled by an inter-
nal baud rate generator or external times 16 clocks. The baud rate
generator accepts either a crystal or a clock input, and provides
15 programmable baud rates. When a 3.6864 MHz crystal is used,
the baud rates range from 50 bps to 38,400 bps.
The DACIA may be programmed to transmit and receive frames
having word lengths of 5, 6, 7 or 8 bits; even, odd, space, mark
or no parity; and 1 or 2 stop bits.
A Compare Register, and the ability to detect address frames, facili-
tate address recognition in a multidrop mode.
• Low power CMOS N-well silicon gate technology
• Two independent full duplex channels with buffered receivers
• Data seUmodem control functions
• Internal baud rate generator with 15 programmable baud rates
(50 bps to 38,400 bps)
• Program-selectable internally or externally controlled receiver
and transmitter bit rates
• Programmable word lengths, number of stop bits, and parity
bit generation and detection
• Programmable interrupt control
• Edge detect for DCD, DSR, and CTS
• Program-selectable echo mode for each channel
• Compare Register
• Address/Data frame recognition
• 5.0 Vdc ±5% supply requirements
• 40-pin plastic or ceramic DIP or 44-pin PLCC
• Full TTL or CMOS inpuUoutput compatibility
• Compatible with R68000 microprocessors
1L T';"",,"~Part Number:
Blank = "O''°'C'''to",+.7.0T°C'"
E = -40°C to +85°C
C = 40-Pin Ceramic DIP
P = 40-Pin Plastic DIP
J = 44-Pin Plastic Leaded
Chip Carrier (PLCC)
Document No. 68650N09
Order No. 708
Rev_ 3, June 1987