Ei68C681 Ei88C681 DUAL UART Semiconductor, Inc. FEATURES DESCRIPTION • Full duplex, dual channel asynchronous receiver and transmitter • Quadruple-buffered receiver and transmitter • Stop bits programmable in 1/16-bit increments • Internal bit rate generator with 23 bit rates • Independent bit rate selection for each Rx and Tx • Maximum bit rate: 1 x clock - 2 Mb/sec., 16 x clock- 250 Kb/sec. • Normal, auto-echo, local loop-back and remote loop-back modes • Multi-function 16-bit counter/timer • Interrupt output with 8 maskable interrupt ing conditions • Interrupt vector output on acknowledge • Programmable interrupt daisy chain • Up to 15 I/O pins (depending on package and version) • Multidrop mode compatible with 8051 ninebit mode • On-chip oscillator for crystal • Stand-by mode to reduce operating power • Advanced CMOS low power technology PIN CONFIGURATION 40-PIN DIP E i 8 8 C 6 8 1 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 40-PIN DIP VCC IP4/IEI IP5/IEO IP6/IACKN IP2 CEN A4 RESET IP0 X2 R/WN X1/CLK DTACK • RXDB RxDA NC TxDA TXDB OP0 OP1 OP2 OP3 OP4 OP5 OP6 OP7 D0 D2 D4 D6 INTRN A2 IP1 A2 IP3 A1 NC VCC IP4/IEI IP5/IEO IP6/IACK IP2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 6 5 4 3 2 6 5 4 3 2 1 44 43 42 41 40 A0 IP3 A1 IP1 A2 A3 IPO WRN RDN RxDB TxDB OP1 OP3 OP5 OP7 D1 D3 D5 D7 GND 1 44 43 42 41 40 7 39 8 38 9 37 36 10 35 11 12 Ei68C681 34 13 33 14 32 15 31 30 16 29 17 18 19 20 21 22 23 24 25 26 27 28 44-PIN PLCC CS • RESET X2 X1/CLK • RXDA NC TXDA OP0 OP2 OP4 OP6 A3 IP0 WR• RD• RXDB NC TXDB OP1 OP3 OP5 OP7 7 8 9 10 11 12 13 14 15 16 17 Ei88C681 39 38 37 36 35 34 33 32 31 30 29 CE• RESET X2 X1/CLK• RXDA NC TXDA OP0 OP2 OP4 OP6 18 19 20 21 22 23 24 25 26 27 28 VCC IP4 IP5 IACK• IP2 CS• RESET• X2 X1/CLK RxDA TxDA OP0 OP2 OP4 OP6 D0 D2 D4 D6 INTR• D1 D3 D5 D7 GND NC INTR D6 D4 D2 D0 E i 6 8 C 6 8 1 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 Part Numbers May Be Marked With "IMP" or "Ei." A3 IP1 A2 IP3 A1 NC VCC IP4 IP5 IACKN IP2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Two basic versions of the DUART are available, each optimized for use with various microprocessor families: the 88C81 for 8085/85, 8080/88, Z80, Z8000, 68XX and 65XX family based systems., and the 68C681 for 68000 family based systems. A programmable mode of the Ei88C681 versions provides an interrupt daisy chain for use in Z80 and Z8000 based systems. The bus interfaces are however general enough to allow interfacing with other microprocessors and microcontrollers. The 88C681 and 68C681 are enhanced versions of the Signetics 2681 and the Motorola 68681, and are pin and function compatible with those devices. Each channel of the DUART may be independently programmed for operating mode and data format. The operating speed of each receiver and transmitter can beselected from baud rate generator, from the multi-purpose on chip counter/timer or from an external 1 x or 16 x clock.The bit rate generator can operate directly from a crystal connected across two pins or from an external clock. The ability to independently program the operating speed of the receiver and transmitter of each channel makes the DUART attractive for split-speed channel application such as clustered terminal systems. Both receive and transmit data is quadruple-buffered in on-chip FIFO to minimize the risk of receiver overrun or to reduce overhead in interrupt-drive applications. D1 D3 D5 D7 GND NC INTRN D6 D4 D2 D0 A1 IP3 A2 IP1 A3 A4 IPO R/W• DTACK• RxDB TxDB OP1 OP3 OP5 OP7 D1 D3 D5 D7 GND The Epic Ei88C681/Ei68C681 DUART Dual Universal Asynchronous Receiver and Transmitter is a data communication device that provides two fully independent full duplex asynchronous communication channels in a single package. The DUART is designed for use in microprocessor based systems and may be used in a polled or interrupt driven environment. 44-PIN PLCC 13 For additional information, contact IMP, Inc. at 408.432.9100 or visit www.impweb.com IMP, Inc. acquired Epic products on January 26, 2001. (see press release at http://www.impweb.com/PRESS/PR012601.htm) Ei68C681 Ei88C681 DUAL UART Semiconductor, Inc. The DUART provides a flow control capability to inhibit transmission from a remote device when the buffer of the receiving DUART is full, thus preventing loss of data. The DUART also provides a general purpose 16bit counter/timer (which may also be used as a programmable bit rate generator), a multipurpose input port and a multipurpose output port. These ports 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. The Ei68C681 are fabricated using Epic’s advanced CMOS process to provide high performance and low power consumption. BLOCK DIAGRAM 8 D0-D7 OPERATION CONTROL R/W• ADDRESS DECODE DTACK• CE• A0-A3 RESET• INTR• BUS BUFFER R/W CONTROL TRANSMIT LOGIC TxDA RECEIVE LOGIC RxDA 4 INTERRUPT CONTROL IMR IACK• CHANNEL TxDB CHANNEL B (AS ABOVE) RxDB ISR IVR INPUT PORT 6 IP0-IP6 IPCR ACR X1/CLK X2 TIMING AND CONTROL LOGIC OUTPUT PORT 8 OPCR OPR VCC GND 14