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Presented by:-Gaurav SaraswatAssociate Designing Engineer at Tevatron Technology
Basics of serial CommunicationParallel: expensive - short distance – fast – no modulationSerial :cheaper– long (two differ...
Basics of serial communication
Packaging DataStart and stop bitsIn asynchronous transmissionWhen there is no transfer the signal is highTransmission beg...
RS232 Standard1 DCD2 RD3 TD4 DTR5 GND6 DSR7 RTS8 CTS9 RI Create in 1960 and updated in 1969 Logic 1 : -3 to -25 volt Lo...
MAX232 or MAX233
SBUF registerMOV SBUF,#’D’ ;load SBUF=44H, ASCII for ‘D’MOV SBUF,A ;copy accumulator into SBUFMOV A,SBUF ;copy SBUF into a...
Serial control (SCON) RegisterSM2 : used for multi processor communicationREN : receive enable (by software enable/disable...
Mode of operation Mode 0 : Serial data enters and exits through RxD TxD outputs the shift clock. 8 bits are transmitte...
Timing of send in mode 0One machine cycleoscillator cycleRXD (data)TXD (clock pulse)MOV SCON,#0001xxxxBWait: JNB RI,WAITCL...
Mode of operation Mode 1 Ten bits are transmitted (through TxD) or received (through RxD)(A start bit (0), 8 data bits (...
TimermodesGATE C/T M1 M0 GATE C/T M1 M0Timer 1 Timer 0(MSB) (LSB)
Programming for sending data( in mode 1 )4. SETB TR15. MOV SBUF, DATA6. WAIT: JNB TI,WAIT7. CLR TIBAUD RATE VALUE IN TH VA...
Programming for sending data( in mode 1 )MOV TMOD,#20H ;TIMER 1 MODE 2MOV TH1,#-3 ;9600 BAUDMOV SCON,#50H ;REN enableSETB ...
Programming for recieving data( in mode 1 )MOV TMOD,#20H ;TIMER 1 MODE 2MOV TH1,#-3 ;9600 BAUDMOV SCON,#50H ;REN enableSET...
Mode of operation Mode 2 : Eleven bits are transmitted (through TxD), received (through RxD) A start bit (0) 8 data bi...
Mode of operation
What is SMOD Bit 7 of PCON register If SMOD=1 double baud rate PCON is not bit addressable How to set SMODMov a, pconS...
Power control register
Power control A standard for applications where power consumptionis critical two power reducing modes Idle Power down
Idle mode An instruction that sets PCON.0 causes Idle mode Last instruction executed before going into the Idle mode th...
Power-Down Mode An instruction that sets PCON.1 causes power dowm mode Last instruction executed before going into the p...
Power control exampleOrg 0000hLjmp mainOrg 0003hOrl pcon,#02h ;power down modeRetiOrg 0030hMain:………………Orl pcon,#01h ;Idle ...
example
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  1. 1. Presented by:-Gaurav SaraswatAssociate Designing Engineer at Tevatron Technology
  2. 2. Basics of serial CommunicationParallel: expensive - short distance – fast – no modulationSerial :cheaper– long (two different cities by modem)-slow
  3. 3. Basics of serial communication
  4. 4. Packaging DataStart and stop bitsIn asynchronous transmissionWhen there is no transfer the signal is highTransmission begins with a start (low) bitLSB firstFinally 1 stop bit (high)Data transfer rate (baud rate) is stated in bps
  5. 5. RS232 Standard1 DCD2 RD3 TD4 DTR5 GND6 DSR7 RTS8 CTS9 RI Create in 1960 and updated in 1969 Logic 1 : -3 to -25 volt Logic 0 : 3 to 25 volt To Connect TXD to RXD and RXD to TXD frompc to 8051 you must use max232 to convertsignal from TTL level to RS232 level The baud rate of the 8051 must matched thebaud rate of the pc PC standard baud rate (see hyper terminalconfiguration) 2400-4800-9600-14400-19200-28800-33600-57600
  6. 6. MAX232 or MAX233
  7. 7. SBUF registerMOV SBUF,#’D’ ;load SBUF=44H, ASCII for ‘D’MOV SBUF,A ;copy accumulator into SBUFMOV A,SBUF ;copy SBUF into accumulator
  8. 8. Serial control (SCON) RegisterSM2 : used for multi processor communicationREN : receive enable (by software enable/disable)TB8 : transmit bit8RB8 : receive bit 8TI : transmit interrupt flag set by HW after send , clear by SWRI : receive interrupt flag set by HW after received ,clear by SWSM0 RITIRB8TB8RENSM2SM17 6 5 4 3 2 1 0SM0 SM1 MODE operation transmit rate0 0 0 shift register fixed (xtal/12)0 1 1 8 bit UART variable (timer1)1 0 2 9 bit UART fixed (xtal/32 or xtal/64)1 1 3 9 bit UART variable (timer1)SM0 : mode specifierSM1 : mode specifier
  9. 9. Mode of operation Mode 0 : Serial data enters and exits through RxD TxD outputs the shift clock. 8 bits are transmitted/received(LSB first) The baud rate is fixed a 1/12 the oscillator frequency. Application Port expansion8051TXDRXD Shift registerclkdata
  10. 10. Timing of send in mode 0One machine cycleoscillator cycleRXD (data)TXD (clock pulse)MOV SCON,#0001xxxxBWait: JNB RI,WAITCLR RIMOV A,SBUFMOV SCON,#0001xxxxBWait: JNB TI,WAITCLR TIMOV SBUF,A
  11. 11. Mode of operation Mode 1 Ten bits are transmitted (through TxD) or received (through RxD)(A start bit (0), 8 data bits (LSB first), and a stop bit (1) ) On receive, the stop bit goes into RB8 in SCON the baud rate is determined by the Timer 1 overflow rate. Timer1 clock is 1/32 machine cycle (MC=1/12 XTAL)• Timer clock can be programmed as 1/16 of machine cycle• Transmission is initiated by any instruction that uses SBUF as adestination register.
  12. 12. TimermodesGATE C/T M1 M0 GATE C/T M1 M0Timer 1 Timer 0(MSB) (LSB)
  13. 13. Programming for sending data( in mode 1 )4. SETB TR15. MOV SBUF, DATA6. WAIT: JNB TI,WAIT7. CLR TIBAUD RATE VALUE IN TH VALUE IN HEX9600 -3 FD4800 -6 FA2400 -12 F41200 -24 E8XTAL=11.0592 MHzGATE C/T M1 M0 GATE C/T M1 M0Timer 1 Timer 0(MSB)(LSB)1. MOV TMOD,#20H2. MOV TH1,# baud rate3. MOV SCON,#50HSM0 RITIRB8TB8RENSM2SM1
  14. 14. Programming for sending data( in mode 1 )MOV TMOD,#20H ;TIMER 1 MODE 2MOV TH1,#-3 ;9600 BAUDMOV SCON,#50H ;REN enableSETB TR1 ;start timer1AGAIN: MOV SBUF, # “A”WAIT: JNB TI,WAITCLR TISJMP AGAINSerial example(1)
  15. 15. Programming for recieving data( in mode 1 )MOV TMOD,#20H ;TIMER 1 MODE 2MOV TH1,#-3 ;9600 BAUDMOV SCON,#50H ;REN enableSETB TR1 ;start timer1WAIT: JNB RI,WAITMOV A,SBUFCLR RISJMP WAITSerial example(2)
  16. 16. Mode of operation Mode 2 : Eleven bits are transmitted (through TxD), received (through RxD) A start bit (0) 8 data bits (LSB first) A programmable 9th data bit and a stop bit (1) On transmit, the 9th bit (TB8) can be assigned 0 or 1. On receive, the 9the data bit goes into RB8 in SCON. the 9th can be parity bit The baud rate is programmable to 1/32 or 1/64 the oscillator frequency inMode 2 by SMOD bit in PCON register Mode 3 Same as mode 2 But may have a variable baud rate generated from Timer 1.
  17. 17. Mode of operation
  18. 18. What is SMOD Bit 7 of PCON register If SMOD=1 double baud rate PCON is not bit addressable How to set SMODMov a, pconSetb acc.7Mov pcon,a
  19. 19. Power control register
  20. 20. Power control A standard for applications where power consumptionis critical two power reducing modes Idle Power down
  21. 21. Idle mode An instruction that sets PCON.0 causes Idle mode Last instruction executed before going into the Idle mode the internal CPU clock is gated off Interrupt, Timer, and Serial Port functions act normally. All of registers , ports and internal RAM maintain their data during Idle ALE and PSEN hold at logic high levels Any interrupt will cause PCON.0 to be cleared by HW (terminate Idle mode) then execute ISR with RETI return and execute next instruction after Idle instruction. RST signal clears the IDL bit directly
  22. 22. Power-Down Mode An instruction that sets PCON.1 causes power dowm mode Last instruction executed before going into the power downmode the on-chip oscillator is stopped. all functions are stopped,the contents of the on-chip RAMand Special Function Registers are maintained. The ALE and PSEN output are held low The reset that terminates Power Down
  23. 23. Power control exampleOrg 0000hLjmp mainOrg 0003hOrl pcon,#02h ;power down modeRetiOrg 0030hMain:………………Orl pcon,#01h ;Idle modeend
  24. 24. example

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