Range of Values of Digital Quantities

To be able to process analog quantities digitally, they have to be converted into digital values.

1 Bit =>	21 states	=	2  values
2 Bits =>	22	=	4 values
3 Bits =>	23	=	8 values
4 Bits =>	24	=	16  values
8 Bits =>	28	=	256  values
12 Bits =>	212	=	4096  values
16 Bits =>	216	=	65536  values
20 Bits =>	220	=	1048576  values

Transmission of Digital Signals

Digital data can be transmitted between one or several devices or communication participants by two ways, either parallel or serial transmission.

• Bit-parallel transmission
• Bit-serial transmission

Parallel data transmission

Serial data transmission

 All bits of a piece of information are transmitted at the same time, with parallel transmission,– through an appropriate number of signal lines. Due to it's high installation costs they are only acceptable for short distances. The transmission of one byte requires a minimum of nine lines,– 8 of which are bits and one is reference potential. This method is presently used for device busses. This application –requires high transmission rates over short distances, and without conversion methods. Serial transmission is a good solution for long distances. Only one signal line in serial transmission method transmits the bits, one after the other. The transmission of information takes more time. The installation effort and the costs are considerably reduced because all the information is generated and processed in bit-parallel mode. The transmitter converts the data from parallel to serial, and the receiver reconverts it from serial to parallel. This is performed by specially operated shift registers, integrated in communication modules.

Bits and Bytes In Hexadecimal Notation

Digital technology groups 8 bits together to form a byte. It does not very often operate with the smallest possible digital quantity.

Since 8 bits is 1 byte, therefore 8, 16 or 32 bit units are termed accordingly 1, 2 or 4 byte units. When it comes to larger range of values, like 2-byte variable: 01101001 00001101, the binary system with its 0’s and 1’s soon becomes unclear. So inorder to achieve clarity, hexadecimal system can be used. In this numbering system, each character can assume 16 different values: 0 to 9 and A to F.

Binary and hexadecimal representation of a 4-bit unit

 

	Hexadecimal	Binary
	0	0000
	1	0001
	2	0010
	3	0011
	4	0100
	5	0101
	6	0110
	7	0111
	8	1000
	9	1001
	A	1010
	B	1011
	C	1100
	D	1101
	E	1110
	F	1111

Signal Formats

The most common signal formats are as follows:

• Non-Return-to-Zero (NRZ)
• Delayed Non-Return-to-Zero (DNRZ)
• Return-to-Zero (RZ)
• Return-to-One (R1)

For NRZ the waveform switches to a “1” and stays at that value until the next cycle boundary, when a valid bit occurs in the cycle. For DNRZ Similar to NRZ, the waveform switches to a “1” after a specified delay time, when a valid bit occurs in the cycle. For RZ the waveform switches to a “1,” then back to a “0” within the same cycle, when a valid bit occurs in the cycle. R1  assumes the cycle begins with a “1”, then switches to a “0” when the bit is valid, then switches back to a “1” before the cycle ends.