1. AT24CS64-XHM-T Substitution Conclusion This device is a viable drop-in replacement with high feasibility. Its core specifications — including capacity, interface, voltage range, package, and write cycle time — are identical to those of the original part. The only quantifiable deviation is the access time, which increases slightly from 400 ns to 550 ns. Under continuous read operations at the maximum clock rate of 1 MHz, this will result in a minor theoretical reduction in peak throughput. However, for the vast majority of I2C bus applications — which are typically limited by protocol overhead rather than nanosecond-scale access times — this difference is imperceptible in practice and does not affect functional performance.