The datasheet for the CY7C0853V does not include an ISB value for the CY7C0853V, although it does exist for the CY7C0850V, CY7C0851V, CY7C0852V. The reason is that you cannot actually disable the ports on the CY7C0853V. Both ports are always enabled (see note 18 of the datasheet).
If stand-by power is a concern for your design, there are certain ways to reduce the "typical" active power of this particular dual-port. For example, if you are not actively reading or writing into either port, you can disable the clock inputs for both ports. Also, disabling all byte select inputs (B0#-B3#) isolates the dual-port memory array from input lines. This places input data lines to become "don't care" signals and hence toggling inputs do not trigger switching activities in the core. In addition, set OE# signal high, thereby disabling the outputs. Finally, leave R/W# high, as the logic for a write operation consumes more power than a read operation.