Hi Sumedh,

this can not work, how expected.
The OC pin must be always active. It is the output enable !

You must combine /WR and chip select together, so that data only clocked in, if both active.
E.g. use the 74HC139 instead of 74HC138. It have 2 decoders, 1 can be used for RAM/ROM and the other half can be enabled with /WR only.

Or use a latch with clock enable input like 74HC377.


Peter