1. 24FC64T-I/ST Substitution Conclusion From the perspective of core electrical specifications and functionality, the 24FC64T-I/ST serves as a highly viable and performance-enhanced direct substitute for the original part, BR24S64FV-WE2. The two devices are fully aligned on all key parameters, including memory capacity (64Kbit), organization (8K x 8), interface (I2C), operating voltage range (1.7V to 5.5V), and write cycle time (5ms). The primary differences are twofold: 1) The clock frequency is increased from 400kHz to 1MHz. This upgrade enables higher potential data transfer rates on the bus, representing a clear performance improvement, provided the host controller and bus conditions support it. 2) The package changes from an 8-SSOP to an 8-TSSOP. While the body width is identical, the lead pitch may differ slightly (TSSOP typically features a finer pitch). Physical replacement therefore requires verification of PCB pad layout compatibility. Provided the package is acceptable, the substitution is electrically seamless and beneficial.