CHAPTER 6

< Day Day Up >

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CHAPTER 6

1. 
   

   For the bit pattern 10101010100, the NRZ-I waveform is as follows:

   
   
   
   
   
   
   

   The NRZ-L waveform is as follows:
   

   
   
   
   
   
   
   


2. 
   

   For the bit pattern 10101010110, the waveform using Manchester coding is as follows:

   
   
   
   
   
   
   


3. 
   

   For the bit pattern 101010101110, the waveform appear on an RS232 port will appear as:

   
   
   
   
   
   
   


4. 
   

   For the bit pattern 10101010100, bipolar AMI waveform is as follows:

   
   
   
   
   
   
   

   
   The HDB3 waveform is as follows:

   
   
   
   
   
   
   

   Note that the HDB3 encoding will be the same as AMI. When four consecutive zeros are in the bit stream, the waveforms will be different.

   
   


5. 
   

   The UART (universal asynchronous receive-transmit) chip is used to control the serial communication port (COM port) of the PC. The functions of this chip are converting parallel data into serial data and vice versa, adding start and stop bits, creating a hardware interrupt when a character is received, and flow control. Different UART chips support different speeds: 8250 supports 9.6kbps, 16450 supports 19.2kbps, and 16550 supports 115.2kbps. 8250 and 16450 have one byte buffer, and 16550 has 16 bytes of buffer.

   
   


6. 
   

   To generate 5 bit codes from the RS232 interface of your PC is not possible. In RS232 communication, there will be start bit and a parity bit. Even if there are five data bits, additional bits are added. To generate five bit codes, you need to have special hardware with UART chips.