Basic Principle of Store

Basic Principle of Store Points : Basic Principle of Store In the digital system, a large amount of data is required to be stored in the memory and retrieved when desired. The data stored in the memory consists of many words. Each word consists f a sequence of 0’s and 1’s and is stored in a memory location called its address. When a word is entered in the memory, it is said that it has been written into the memory, and when it is located, it has been read. The word that is being written in or read from the memory is called addressing. The switching principles are provided with two types of memories. One is called data memory or slot-content memory and the other is control memory (slot interchange information).

The data memory has as many locations as there are time slots. Each location can accommodate all the bits in a time slot. There is a time slot counter, which runs at the time slot rate and increased its count by one at the end of each time slot. The counter provides the address at which the word is written into the memory. The content of slot 1 is written into memory location 1, the content of slot 2 into memory location 2 etc. The contents of successive slots are written into the memory sequentially.

The control memory holds the addresses of the data memory from which words are to be read. The control memory has as many locations as needed to accommodate bits to write the number of incoming signals. A time slot counter provides reading addresses for the control memory.

For example in figure, the address 7 has written in memory location 1 of the control memory. Now during the first time slot of the frame, the content of slot 1 will be written into the data memory but during this time the word in memory location 7 will be read from the memory. It is the content of slot 7. Hence the contents of slot I and 7 have been interchanged. Thus the transmitting subscriber 7 has been switched to receiving subscriber 1.