INTEGRATED CIRCUITS SCC2681 Dual asynchronous receiver/transmitter (DUART) Product data 2004 Apr 06
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 • 16-bit programmable Counter/Timer 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. It interfaces directly with microprocessors and may be used in a polled or interrupt driven system.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 PIN CONFIGURATIONS INDEX CORNER A0 1 40 VCC IP3 2 39 IP4 A1 3 38 IP5 IP1 4 37 IP6 A2 5 36 IP2 6 35 CEN IP0 7 34 RESET WRN 8 33 X2 32 X1/CLK 31 RXDA RXDB 10 30 TXDA 29 OP0 OP1 12 13 28 OP2 OP5 14 27 OP4 OP3 26 OP6 OP7 15 D1 16 25 D0 D3 17 24 D2 D5 18 23 D4 D7 19 22 D6 GND 20 A0 1 28 VCC A1 2 27 IP2 A2 3 26 CEN A3 4 25 RESET WRN 5 24 X2 RDN 6 23 X1/CLK RXDB
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SYMBOL PIN TYPE SCC2681 NAME AND FUNCTION PLCC44 DIP40 DIP28 X2 37 33 24 I Crystal 2: Crystal connection. See Figure 7. If a crystal is not used it is best to keep this pin not connected although it must not be grounded. RxDA 35 31 22 I Channel A Receiver Serial Data Input: The least significant bit is received first. “Mark” is HIGH, “space” is LOW.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 ABSOLUTE MAXIMUM RATINGS1 PARAMETER SYMBOL RATING UNIT Tamb Operating ambient temperature See Note 4 °C Tstg Storage temperature range –65 to +150 °C All voltages with respect to ground3 –0.5 to +6.0 V VSS – 0.5 V to VCC + 0.5 V V range2 Pin voltage range NOTES: 1. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 AC CHARACTERISTICS Tamb = –40 °C to +85 °C1; VCC = +5.0 V ± 10% 2, 3, 4, 5 SYMBOL LIMITS PARAMETER UNIT Min Typ Max 200 – – ns 10 100 0 0 225 – – 100 20 200 – – – – – – – – – – – – – – – 175 100 – – – ns ns ns ns ns ns ns ns ns ns 0 0 – – – – – – 400 ns ns ns – – – – – – – – – – – – 300 300 300 300 300 300 ns ns ns ns ns ns 100 1.0 100 0 220 0 0 220 0 0 – 3.6864 – – – – – – – – – 4.0 – 4.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 8. Consecutive write operations to the same command register require at least three edges of the X1 clock between writes. 9. This parameter is not applicable to the 28-pin device. 10. Operation to 0 MHz is assured by design. However, operation at low frequencies is not tested and has not been characterized.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 BLOCK DIAGRAM Counter/Timer (C/T) The SCC2681 DUART consists of the following eight major sections: data bus buffer, operation control, interrupt control, timing, communications Channels A and B, input port and output port. Refer to the block diagram. The counter timer is a 16 bit programmable divider that operates one of three modes: Counter, Timer or Time Out mode.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 Output Port Receiver The output port pins may be controlled by the OPR, OPCR, MR and CR registers. Via appropriate programming they may be just another parallel port to external circuits, or they may represent many internal conditions of the UART. When this 8-bit port is used as a general purpose output port, the output port pins drive a state which is the complement of the Output Port Register (OPR).
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) or MR1B[4:3] to ‘11’ for Channels A and B, respectively. In this mode of operation, a ‘master’ station transmits an address character followed by data characters for the addressed ‘slave’ station. The slave stations, with receivers that are normally disabled, examine the received data stream and ‘wake up’ the CPU (by setting RxRDY) only upon receipt of an address character.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 PROGRAMMING Mode registers 1 and 2 of each channel are accessed via independent auxiliary pointers. The pointer is set to MR1x by RESET or by issuing a ‘reset pointer’ command via the corresponding command register. Any read or write of the mode register while the pointer is at MR1x, switches the pointer to MR2x.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 Table 2.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 Table 2.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 MR1A – Channel A Mode Register 1 MR2A – Channel A Mode Register 2 MR1A is accessed when the Channel A MR pointer points to MR1. The pointer is set to MR1 by RESET or by a ‘set pointer’ command applied via CRA. After reading or writing MR1A, the pointer will point to MR2A. MR2A is accessed when the Channel A MR pointer points to MR2, which occurs after any access to MR1A.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) or transmitted character. Likewise, if a mode is deselected the device will switch out of the mode immediately.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) CSRA[7:4] – Channel A Receiver Clock Select This field selects the baud rate clock for the Channel A receiver as follows (X1 rate at 3.6864 MHz): CSRA[7:4] ACR[7] = 0 Baud Rate ACR[7] = 1 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 50 110 134.5 200 300 600 1,200 1,050 2,400 4,800 7,200 9,600 38.4k Timer IP4–16× IP4–1× 75 110 134.5 150 300 600 1,200 2,000 2,400 4,800 1,800 9,600 19.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) receive shift register waiting for an empty FIFO position. When this occurs, the character in the receive shift register (and its break detect, parity error and framing error status, if any) is lost. CRB – Channel B Command Register CRB is a register used to supply commands to Channel B. Multiple commands can be specified in a single write to CRB as long as the commands are non-conflicting, e.g.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 OPCR – Output Port Configuration Register ACR – Auxiliary Control Register OPCR[7] – OP7 Output Select This bit programs the OP7 output to provide one of the following: 0 – The complement of OPR[7]. 1 – The Channel B transmitter interrupt output which is the complement of TxRDYB. When in this mode OP7 acts as an Open-drain output. Note that this output is not masked by the contents of the IMR.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) become full; i.e., all three FIFO positions are occupied. It is reset when the CPU reads the RHR. If a character is waiting in the receive shift register because the FIFO is full, the bit will be set again when the ISR[0] and IMR waiting character is loaded into the FIFO. ISR – Interrupt Status Register This register provides the status of all potential interrupt sources.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) masked off through the OPCR[3:2] = 00 until the T/C is programmed to the desired operational state. SCC2681 The CTS, RTS, CTS Enable Tx signals CTS (Clear To Send) is usually meant to be a signal to the transmitter meaning that it may transmit data to the receiver. The CTS input is on pin IP0 for TxA and on IP1 for TxB. The CTS signal is active LOW; thus, it is called CTSAN for TxA and CTSBN for TxB.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 Table 5. Baud Rates Extended Normal BRG BRG Extended Rates CSR[7:4] ACR[7] = 0 ACR[7] = 1 ACR[7] = 0 ACR[7] = 1 0000 50 75 4,800 7,200 0001 110 110 880 880 0010 134.5 134.5 1,076 1,076 0011 200 150 19.2 k 14.4 k 0100 300 300 28.8 k 28.8 k 0101 600 600 57.6 k 57.6 k 0110 1,200 1,200 115.2 k 115.2 k 0111 1,050 2,000 1,050 2,000 1000 2,400 2,400 57.6 k 57.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 TIMING DIAGRAMS RESET tRES SD00086 Figure 3. Reset Timing A0–A3 tAS tAH CEN tCS tCH tRW tRWD RDN tDD D0–D7 (READ) tDF NOT VALID FLOAT VALID FLOAT tRWD WDN tDS tDH D0–D7 (WRITE) VALID SD00087 Figure 4. Bus Timing RDN tPS tPH IP0–IP6 WRN tPD VOH OP0–OP7 OLD DATA VM NEW DATA VOL VM = 1.5V SD00089 Figure 5.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 TIMING DIAGRAMS (Continued) RDN OR WRN VM tIR VOL INTERRUPT 1 OUTPUT +0.5V VOL NOTES: 1. INTRN or OP3 – OP7 when used as interrupt outputs. 2. The test for open-drain outputs is intended to guarantee switching of the output transistor. Measurement of this response is referenced from themidpoint of the switching signal, VM, to a point 0.5V above VOL.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 1 BIT TIME (1 OR 16 CLOCKS) TxC (INPUT) tTXD TxD tTCS TxC (1X OUTPUT) SD00092 Figure 8. Transmit TIMING DIAGRAMS (Continued) RxC (1X INPUT) tRXS tRXH RxD SD00093 Figure 9. Receiver Timing TxD D1 D2 D3 BREAK D4 D6 TRANSMITTER ENABLED TxRDY (SR2) WRN D1 D2 D3 START BREAK D4 CTSN1 (IP0) STOP BREAK D5 WILL NOT BE TRANSMITTED D6 RTSN2 (OP0) OPR(0) = 1 OPR(0) = 1 NOTES: 1.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 TIMING DIAGRAMS (Continued) D1 RxD D2 D3 D4 D5 D6 D7 D8 D6, D7, D8 WILL BE LOST RECEIVER ENABLED RxRDY (SR0) FFULL (SR1) RxRDY/ FFULL (OP5)2 RDN STATUS DATA STATUS DATA STATUS DATA STATUS DATA D5 WILL BE LOST D1 OVERRUN (SR4) D2 D3 D4 RESET BY COMMAND RTS1 (OP0) OPR(0) = 1 NOTES: 1. Timing shown for MR1(7) = 1. 2. Shown for OPCR(4) = 1 and MR(6) = 0. SD00095 Figure 11.
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) DIP28: plastic dual in-line package; 28 leads (600 mil) 2004 Apr 06 26 SCC2681 SOT117-1
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) DIP40: plastic dual in-line package; 40 leads (600 mil) 2004 Apr 06 27 SCC2681 SOT129-1
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) PLCC44: plastic leaded chip carrier; 44 leads 2004 Apr 06 SCC2681 SOT187-2 28
Philips Semiconductors Product data Dual asynchronous receiver/transmitter (DUART) SCC2681 REVISION HISTORY Rev Date Description _1 20040406 Product data (9397 750 12075). ECN 853-2445 01-A15014 of 15 December 2003. Data sheet status Level Data sheet status [1] Product status [2] [3] Definitions I Objective data Development This data sheet contains data from the objective specification for product development.
