1. The data message defined by 9A73(hexadecimal) is to be transmitted over a ser
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Question
1. The data message defined by 9A73(hexadecimal) is to be transmitted over a serial link at a rate of 9600 bps. The message is delivered in “MSB first,” 9-bit format which includes the data byte plus the odd parity bit. Sketch the voltage waveform if NRZ encoding is used for line coding. The NRZ code is bi-polar with B = 5 volts.
2. Sketch the waveform of the 1000 bps data pattern 58D (hexadecimal) using Manchester code. The amplitude of the symbols is 12 volts.
3. Sketch the waveform of the word 1101 1011 0011 0110 if transmitted using quad quam. The data rate is 4 kbps and the amplitude scaling factor for symbols is 0.25.
Explanation / Answer
Line coding consists of representing the digital signal to be transported, by a waveform that is optimally tuned for the specific properties of the physical channel (and of the receiving equipment). The pattern of voltage, current or photons used to represent the digital data on a transmission link is called line encoding. The common types of line encoding are unipolar,polar, bipolar, and Manchester encoding.
Bipolar non-return-to-zero level[edit]
"One" is represented by one physical level (usually a positive voltage), while "zero" is represented by another level (usually a negative voltage). In clock language, in bipolar NRZ-Level the voltage "swings" from positive to negative on the trailing edge of the previous bit clock cycle.
An example of this is RS-232, where "one" is 12 V to 5 V and "zero" is +5 V to +12 V.
Non return to zero, inverted (NRZI) is a method of mapping a binary signal to a physical signal for transmission over some transmission media. The two level NRZI signal has a transition at a clock boundary if the bit being transmitted is a logical 1, and does not have a transition if the bit being transmitted is a logical 0.
"One" is represented by a transition of the physical level, while "zero" has no transition. Also, NRZI might take the opposite convention, as in Universal Serial Bus (USB) signalling, when in Mode 1, in which a transition occurs when signaling zero, and a steady level when signaling a one. The transition occurs on the leading edge of the clock for the given bit. This distinguishes NRZI from NRZ-Mark.
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