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Lecture # 13

Lecture # 13. C:>debug -o 378 0A -i 379 D0 -o 378 19 -i 379 48. Sending byte 9A. C:>debug -i 379 D7 -o 378 0A -i 379 4F -o 378 19.

duncan-bernard
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Lecture # 13

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  1. Lecture # 13

  2. C:\>debug-o 378 0A-i 379D0-o 378 19-i 37948 Sending byte 9A C:\>debug-i 379D7-o 378 0A-i 3794F-o 378 19

  3. 0A=00001010 , Data line 4=0 (sent)D7=11010111 , BUSY=1 (recieved)11010111 >> 3 = 00011010 00011010 & 00001111 = 00001010 = 0A , Data line 4 =0 (send for verification)D0 = 11010000 , BUSY=1 (received & verified)

  4. 09=00001001 , Data line 4 =0Set Data line 4 to 100001001 | 00010000 = 00011001 = 19 ,(Sent to 378H) (Sent)4FH=01001111 , BUSY=0 (Received)01001111 << 1 = 1001111

  5. Joining both nibblesLow Nibble00011010 & 00001111 = 00001010Hi Nibble10011111 & 11110000 = 10010000Whole byte00001010 | 10010000 = 10011010 = 9A

  6. int i= 0; char Buf[1024]; while (1) { ch = Buf [i]; if ((inport((*lpt) + 1)& 0x80) == 0) { ch = Buf [i]; ch = ch & 0xEF; while((inport((*lpt) + 1) &0x80) == 0); } else { ch = Buf [i]; ch = ch >> 4; ch = ch | 0x10; outport (*lpt, ch); i++; while((inport((*lpt) + 1) &0x80) == 80); } }

  7. int i; while (1) { if ((inport(*lpt + 1)& 0x80) == 0x80) { x = inport ((*lpt) + 1); x = x >> 3; x = x & 0x0F; outport((*lpt), x); while((inport(*lpt + 1) &0x80) == 0x80); } else { y = inport ((*lpt) + 1); y = y << 1; temp = y; y = y | x;

  8. temp = temp >> 4; \\ Move to Low Nibble temp = temp | 0x10;\\ Set D4 bit i++; outport (*lpt, temp);\\ Send for verification Buf [i] = y; while((inport((*lpt) + 1) &0x80) == 0); } }

  9. Serial Communication • Advantages • Disadvantages

  10. Types Of Serial Communication • Synchronous • Asynchronous

  11. LSB MSB 1 1 0 1 0 1 1 0 Synchronous Communication • Timing signal is used to identify start and end of a bit. 0 1 1 0 1 0 1 1

  12. Synchronous Communication • Sampling may be edge triggered. • Special line may be required for timing signal (requires another line). • Or the timing signal may be encoded within the original signal (requires double the bandwidth).

  13. Asynchronous Communication • Does not use make use of timing signal. • Each byte (word) needs to encapsulated in start and end bit.

  14. Serial Communication using a UART Parity bit Start bit of next byte 0 1 2 3 4 5 6 7 8 1 0 5 – 8 bit 1, 1.5, 2 Stop bit Start bit • 1.5 Stop bit

  15. Sampling Rate Bit rate = 9600 A bit is sampled after = 1/9600 -- But start and end bits of a particular Byte cannot be recognized. -- So 1.5 stop bit (high) is used to encapsulate a byte. A start bit (low) at the start of Byte is used to identify the start of a Byte.

  16. Sampling Rate • -- Bit rate and other settings should be the same at both ends i.e. • Data bits per Byte. (5 – 8 ) • Parity check • Parity Even/Odd • No. of stop bits.

  17. Sampling Rate 1/1300 sec Data bits Stop bit Start bit Odd parity A = 41H = 0100 0001 B Parity = Odd Data = 8 Stop bit =1 Data rate = 300 bits/sec

  18. RS – 232C Standard • Standard for physical dimensions of the connectors. RS – 232C Cable PC (DTE) (DCE) Modem Connected via serial port

  19. RS – 232C Connectors and SignalsDB25 (25 pin connector) 13 25 12 24 11 23 10 RI 22 9 21 CD 8 DTR 20 GND 7 19 6 DSR 18 5 CTS 17 4 RTS 18 3 RD 19 2 T X D 20 1 25 pin connector on PC

  20. RI CD DTE DCE DTR MODEM PC DSR RTS CTS RxD TxD DTR (SHOULD REMAIN HIGH THROUGH OUT THE SESSION ) CTS (CAN BE USED FOR FLOW CONTROL )

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