單片機(jī)飛思卡爾SCI模塊

1、異步串行通信（SCI）通信基礎(chǔ)知識(shí)異步串行通信協(xié)議RS-232標(biāo)準(zhǔn)SCI功能簡(jiǎn)介SCI寄存器SCI軟件開發(fā)方法SCI應(yīng)用程序示例Lecture4 Page 1Communications通信方式的幾個(gè)要素串行、并行（Serial/parallel）同步、異步（Synchronous/asynchronous）點(diǎn)對(duì)點(diǎn)、總線（Point-to-point/bus）半雙工、全雙工（Half-duplex/full-duplex）主從式、對(duì)等式（Master-slave/equal partners）單端信號(hào)、差分信號(hào)（Single-ended/differential）通信基礎(chǔ)知識(shí)Lecture4

2、Page 2Communications -characteristics串行通信數(shù)據(jù)按位傳輸通信方只需要很少的連接 resource/pin efficient速度較慢，傳輸信息少傳輸距離較遠(yuǎn)并行通信數(shù)據(jù)按字節(jié)/字傳輸通信方需要多個(gè)連接信號(hào)- difficult for PCB routing傳輸速度快傳輸距離較短你接觸過(guò)哪些串行/并行通信？ 通信基礎(chǔ)知識(shí) 串行、并行Lecture4 Page 3Communications -characteristics同步通信接收方可以得到發(fā)送方的通信時(shí)鐘信號(hào)傳輸速率高異步通信發(fā)送方和接收方使用獨(dú)立的時(shí)鐘來(lái)處理通信信號(hào)通信雙方約定通信速率通信中需要約定

3、起始/停止位或定義特殊的幀結(jié)構(gòu)傳輸速率較低 通信基礎(chǔ)知識(shí) 同步、異步Lecture4 Page 4Communications -characteristics點(diǎn)對(duì)點(diǎn)通信線路上只有兩個(gè)通信方 不需要尋址總線通信線路上有多個(gè)通信方需要建立尋址機(jī)制 通信基礎(chǔ)知識(shí) 拓?fù)浣Y(jié)構(gòu)Lecture4 Page 5Communications -characteristics半雙工不能同時(shí)進(jìn)行發(fā)送和接收一方發(fā)送時(shí)，其他通信方只能處于接收狀態(tài)需要額外的邏輯來(lái)控制發(fā)送和接收狀態(tài)的切換有發(fā)生沖突的危險(xiǎn)全雙工通信端可以同時(shí)進(jìn)行發(fā)送和接收需要兩個(gè)獨(dú)立的通信通道使用簡(jiǎn)單，數(shù)據(jù)傳輸率高對(duì)講機(jī)？電話機(jī)？ 通信基礎(chǔ)知識(shí) 半雙工、

4、全雙工Lecture4 Page 6Communications -characteristics主從式只有主端可以發(fā)起數(shù)據(jù)傳輸從端等待主端的允許才能傳輸數(shù)據(jù)對(duì)等式任何節(jié)點(diǎn)可以發(fā)起數(shù)據(jù)傳輸需要建立沖突檢測(cè)和仲裁機(jī)制 通信基礎(chǔ)知識(shí) 主從式、對(duì)等式Lecture4 Page 7Communications -characteristics單端信號(hào)信號(hào)幅度以地電平作為參考通信雙方必須建立共同的參考地電平干擾造成的信號(hào)幅度變化可能導(dǎo)致錯(cuò)誤解釋差分信號(hào)每個(gè)信號(hào)使用兩根線傳輸，信號(hào)的值由兩個(gè)線上的電平的差值表示通信方不需要共同的參考地對(duì)干擾抑止能力強(qiáng)傳輸速率高 通信基礎(chǔ)知識(shí) 單端、差分信號(hào)Lecture4

5、 Page 8微控制器常見的通信類型總線類型線數(shù)通信類型多主波特率（bps)器件數(shù)目總線長(zhǎng)度UART2異步No3K-1M2*SPI3同步Y(jié)es1M-10M10板內(nèi)I2C2同步Y(jié)es1M10板內(nèi)CAN2異步Y(jié)es20K-1M128百米公里L(fēng)IN1異步No20K16幾十米Lecture4 Page 9SCILecture4 Page 10EIA RS-232-C美國(guó)電子工業(yè)協(xié)會(huì)正式公布的異步串行通信標(biāo)準(zhǔn)，也是目前最常用的異步串行通信標(biāo)準(zhǔn)，用來(lái)實(shí)現(xiàn)計(jì)算機(jī)與計(jì)算機(jī)之間、計(jì)算機(jī)與外設(shè)之間的數(shù)據(jù)通信 RS-232-C電平采用負(fù)邏輯，即，邏輯1：-3-25V,邏輯0：+3+25V （需要電平轉(zhuǎn)換）RS-23

6、2-C接口標(biāo)準(zhǔn)有22根線，采用標(biāo)準(zhǔn)25芯D型插頭座；PC上使用簡(jiǎn)化的9芯D型插座 多種通信應(yīng)答（握手）方式： 硬件握手，自應(yīng)答，XON/XOFF模式波特率： 300bps 4Mbps， 物理層有多種實(shí)現(xiàn)方式（銅纜，光纜，紅外，無(wú)線，微波）起始位/停止位/數(shù)據(jù)位/奇偶校驗(yàn)/全雙工半雙工模式 廣泛應(yīng)用： Modem，20mA電流環(huán)，RS485 個(gè)人計(jì)算機(jī)都有標(biāo)準(zhǔn)的RS232接口，驅(qū)動(dòng)程序，超級(jí)終端 RS232 standardLecture4 Page 11RS232 standardLecture4 Page 12 簡(jiǎn)化的9芯D型接頭信號(hào)定義（硬件流量控制） DTE DCE 3 TxD out

7、TxD Transmit Data2 RxD in RxD Receive Data5 GND GND 7 RTS out RTS Require To Send8 CTS in CTS Clear To Send6 DSR in DSR Data Set Ready9 DCD in DCD Data Care Detected4 DTR out DTR Data Terminal ReadyRS232 standardLecture4 Page 13簡(jiǎn)化的9芯D型接頭信號(hào)定義（自應(yīng)答方式） DTE / DCE 2 TxD out TxD (Transmit Data )3 RxD in Rx

8、D (Receive Data)7 GND GND (Ground)4 RTS out RTS (Require to Send)5 CTS in CTS (Clear to Send)6 DSR in DSR (Data Terminal Ready)8 DCD in DCD (Data Carry Detected)20 DTR out DTR (Data Set Ready)Ready always, or XON/XOFF protocol, ASCII only!RS232 standardLecture4 Page 14簡(jiǎn)化的9芯D型接頭信號(hào)定義（無(wú)應(yīng)答方式） 1 protecti

9、on ground2 RxD in RxD (Receive Data)3 TxD out TxD (Transmit Data )5 GND GND (Ground)6 DSR in DSR (Data Terminal Ready)7 RTS out RTS (Require to Send)8 CTS in CTS (Clear to Send)9 DCD in DCD (Data Carrier Detected) 4 DTR out DTR (Data Set Ready)No Handshake, should use XON/XOFF protocol,ASCII onlyRS2

10、32 standardLecture4 Page 15RS232 standardTTL level vs. RS232 levelLecture4 Page 16RS232 standardTTL level vs. RS232 levelLecture4 Page 17RS232 standardRS232標(biāo)準(zhǔn)（1962）出現(xiàn)的比TTL（1964）還早需要接口轉(zhuǎn)換芯片MAX232MicrocontrollerDB9TTL/CMOSRS232Lecture4 Page 18Frame format012345678LSBMSBstopidleidlestartUARTNRZ (not ret

11、urn zero) encodingSeveral configurable parametersBaud rate, #data bits, parity, #stop bitsNomenclature: 9600,N81LSB- Least significant bitMSB- Most significant bitParity(stop)Lecture4 Page 19Start/stop 位接受端需要明確數(shù)據(jù)幀的邊界，即該幀從什么時(shí)候開始，什么時(shí)候結(jié)束。數(shù)據(jù)位傳送之前，都要發(fā)送START 位(always 0) (從空閑狀態(tài)開始的下降沿，是START位的開始）在數(shù)據(jù)位傳送結(jié)束后，還

12、要傳送STOP位 (always 1).Lecture4 Page 20數(shù)據(jù)位識(shí)別接受端在其時(shí)鐘上升沿采樣數(shù)據(jù)線電平，以識(shí)別數(shù)據(jù)位的高低狀態(tài)。What is the data transmitted above?Lecture4 Page 21數(shù)據(jù)位識(shí)別Tx_clkRx_clkTxDRxD傳輸過(guò)程會(huì)引起信號(hào)的延遲，會(huì)引入外部干擾導(dǎo)致的噪聲及毛刺Lecture4 Page 22SCI(UART)-oversampling- 通信雙方有約定的通信速率（波特率）- 接受端按照16倍波特率的頻率對(duì)信號(hào)進(jìn)行over samples - 使用其中3個(gè)采樣結(jié)果，通過(guò)3取2的機(jī)制確定實(shí)際的信號(hào)電平狀態(tài)- 如果

13、3個(gè)采樣結(jié)果不一致，noise標(biāo)志會(huì)置起- 接受端在總線進(jìn)入空閑狀態(tài)后，通過(guò)監(jiān)測(cè)下降沿，啟動(dòng)對(duì)起始位的判斷，從而開始整個(gè)數(shù)據(jù)幀的接受。Lecture4 Page 23SCI(UART)-oversamplingLecture4 Page 24SCI- 波特率波特率： bits per second Question1: 按照9600,N81的通信參數(shù)，每秒可以傳送多少個(gè)字節(jié)？Hints: dont forget the start/stop bits.Question2: 對(duì)于一個(gè)總線頻率為16MHz的微控制器，其SCI最高支持的波特率是多少？Lecture4 Page 25波特率誤差容限接受

14、端必須能正確的識(shí)別整個(gè)數(shù)據(jù)幀，從起始位到停止位0/10/10/10/10/10/10/110/101116*(1+8) +9 9Ttx (153/16)Trx 10Ttx clock difference tolerance5%10 9 TransmitterReceiverLecture4 Page 26校驗(yàn)位校驗(yàn)位附加在數(shù)據(jù)幀末尾，用于檢查傳輸過(guò)程中是否發(fā)生了數(shù)據(jù)位錯(cuò)誤。LSBMSBstopstartParityLecture4 Page 27Parity bit偶校驗(yàn) - 所有數(shù)據(jù)位和校驗(yàn)位中，1的數(shù)目是偶數(shù)奇校驗(yàn) -所有數(shù)據(jù)位和校驗(yàn)位中，1的數(shù)目是奇數(shù)Example: what is

15、the even parity for “10011100” what is the odd parity for “01010110”Lecture4 Page 28SCI 可能產(chǎn)生的事件 - Tx Empty (IRQ) - Tx Complete (IRQ)- Rx Full (IRQ)- Idle (IRQ)- Rx Overrun (IRQ)- Noise Error- Framing Error- Parity ErrorLecture4 Page 29SCI 故障Framing Error: 在數(shù)據(jù)幀結(jié)尾沒有收到正確的停止位Receiver overrun: 下一個(gè)數(shù)據(jù)到達(dá)時(shí)，上

16、一個(gè)數(shù)據(jù)還沒有被處理Parity Error: 接受的校驗(yàn)和與協(xié)議規(guī)定的不匹配.Lecture4 Page 30So, are we clear about UART?Lets play a game!I need one volunteerThis volunteer will be a UART sender, all your students will be UART receivers.LSB firstProtocol is 1,N81 (1bit per second)Hand-raise is 1, hand-down is 0Lecture4 Page 31Transmitt

17、er: Receiver:.TDR BUFFERSHIFT REGISTERDATA INDATAOUTT8PARITYGEN.DATA OUTRDR BUFFERSHIFT REGISTERDATAINR8PARITYCHECKSCI 雙緩沖寄存結(jié)構(gòu)發(fā)送和接受都具有雙緩沖結(jié)構(gòu) CPU不能讀寫移位緩沖寄存器CPU僅能訪問數(shù)據(jù)寄存器Lecture4 Page 32.SCI 緩沖結(jié)構(gòu)發(fā)送時(shí)，數(shù)據(jù)自動(dòng)從數(shù)據(jù)寄存器轉(zhuǎn)移到移位寄存器接受時(shí)，數(shù)據(jù)自動(dòng)從移位寄存器轉(zhuǎn)移到數(shù)據(jù)寄存器發(fā)送和接受的數(shù)據(jù)寄存器使用相同的寄存器地址 讀寫該寄存器地址具有不同的含義!Question: whats the functio

18、n of the instructions below while(1) asm LDAA SCI0DR asm STAA SCI0DR Lecture4 Page 33Transmitter block diagramTx data registerTx clock genNote the 16Shift registerParity genControl logicInterrupt request genLecture4 Page 34Receiver block diagramRx data registershift registerRx clock genControl logic

19、Lecture4 Page 35SCI(UART)Lecture4 Page 36SCIBH/L - SCI Baud Rate Control Register必須連續(xù)寫入BDH和BDL寄存器，僅僅寫入BDH沒有作用。Bus clock1 819124M bus clockExercise1: 9600bps wanted， BR = ? BDH = ? BDL = ?Exercise2： the maximum baud rate = ?SCI Registers 1/5Lecture4 Page 37SCCR1 - SCI Control Register 1Address Offset

20、 $0002 1 = 9-BIT DATA 0 = 8-BIT DATA 1 = IDLE LINE WAKE-UP 0 = ADDRESS MARK WAKE-UP 1 = NORMAL IDLE TIME 0 = SHORT IDLE TIME1 = EVEN PARITY0 = ODD PARITY1 = PARITY Enabled0 = PARITY DisabledSCISWAI - SCI Stop in Wait mode 0 = Normal operation 1 = SCI Disabled in Wait modeSCI Registers 2/5Lecture4 Pa

21、ge 38SCICR 2 - SCI Control Register 2ILIE - Idle Line Interrupt Enable1 = IDLE IRQ Enabled0 = IDLE IRQ DisabledTE _ Transmitter Enable 1 = Transmitter Enabled0 = Transmitter DisabledRE Receiver Enable1 = Receiver Enabled0 = Receiver DisabledSBK - Send Break1 = Send Break0 = Terminate BreakRWU - Rece

22、iver Wake-up 1 = Enter Receiver Wake-UP 0 = Exit Receiver Wake-UPTCIE - Transmit Complete Interrupt Enable1 = Transmitter Complete IRQ Enabled0 = Transmitter Complete IRQ DisabledRIE - Receiver Interrupt Enable1 = Receiver IRQ Enabled0 = Receiver IRQ DisabledTIE - Transmitter Interrupt Enable1 = Transmitter IRQ Enabled0 = Transmitter IRQ DisabledSCI Registers 3/5Lecture4 Page 39SCISR 1 - SCI Status Register 1SCI Registers 4/5SCISR 2 - SCI Status Register 2RAF - Receiver Active Status 1 = Receiver Active 0 = Receiver not ActiveBRK13 - Break Transmit Character L