Question

1. How many different characters could be encoded using a six-bit code? 2. What is the numerical difference between ASCI a and ASClI 'AN if you treaj them as hexadecimal (hex) numbers? 3. The ASCII codes for the characters 'O' through '9' are what hex numbers? If an asynchronous frame is used to send ASCII characters in the form of bytes (8 bits), what is the shortest time it could take to send 1000 characters if each bit in a frame is 1 msec long? 4. Suppose an asynchronous frame holds 8 bits of data, a parity bit, and two stop bits (it could happen). Calculate the efficiency of the communication system 5. Suppose a synchronous frame has 16 bits of non-data in the front and a 16-bit BCC at the end. The frame carries 1024 bytes of actual data. Calculate the efficiency of the communication system. 6.

Answer 1

1.

Using 6 bits coding, total of 2⁶ = 64 characters can be encoded.

2.

a = 0x61H

A = 0x41H

3.

0 = 30H

1 = 31H

2 = 32H

3 = 33H

4 = 34H

5 = 35H

6 = 36H

7 = 37H

8 = 38H

9 = 39H

4.

In asynchronous transmission, along with data bits atleast a start and stop bit is sent. Hence a character needs (8 + 2 =10 bits).

To send 1000 characters, 10 x 1000 = 10,000 bits is required to be sent over the channel.

Total time = 10,000 bits x 1 ms = 10,000 ms or 10 seconds

5.

Efficiency = (Data Bits / Total Number of Bits) = 8/11 x100 = 72.72%

6.

(1024 x 8) / (1024 x 8 + 16 bits of non data + 16 bit BCC)

8192 / 8224 = 99.6%