Today tested with different combinations to study the response of Modbus
slave addresses:1, Holding register starting address:0, number of Addresses:50 and working ststus:Proper data

slave addresses:1, Holding register starting address:10, number of Addresses:50 and working ststus:Return zero only

slave addresses:2, Holding register starting address:100, number of Addresses:99 and working ststus:Return zero only

slave addresses:2, Holding register starting address:0, number of Addresses:150 and working ststus:Proper data

Based on the observation, Irrespective of slave address, Starting address must be declare as '0' for getting proper response. Else get '0' as the response.
In case required data stored in the range of address 59100 to 59200 (that is 100 specific registers), we need very high memory

I can't able to understand the need for 'starting address of the modbus'.
Kindly correct me that where i am deviated from the actuals.
Thanks in advance for your valuable time and support.