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5. Information Storage


Memory devices play a major role in ITDL, as their responsibility is to store Z80 assembly language commands for the system and call information.


EPROM 27128A has a capacity of 16kx8. The actual memory capacity required to store the program is approximately 8k bytes but provision of additional 8k is there for future expansions and modifications.


RAM  - two 8kx8 SRAMs are used according to the following calculations.

(Note : it is observed that, approximately a maximum of 500 calls are taken within a period of one month and maximum no of digits of a telephone number is 9) 


T/P No.             Date/Time (dd mm yy Hrs.)             Duration (min. sec.)

071758248         01 08 99 13 22 59                              12 29

9 bytes                       6 bytes                                   2 bytes


\ No of bytes require to store one T/P call                = 9 + 6 + 2 = 17 bytes

\ Memory requirement for 500 calls                          =17 x 500  = 8500 bytes = 8.5 k bytes

\ Capacity of 16k RAMs are used in ITDL for additional storage. This has an additional capacity of 7.5k which provides a call capacity of 1000.


RTC  - DS1742 has built in memory of 2kx8.


Fig. 4 Memory Map


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Last modified: July 13, 2002