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