eMMC operates very similarly to an SD card but with an embedded type design. The host interface, or customer’s device, controls all data transmission between host and card, and variable clock frequencies can be set to achieve certain read and write speeds. The 153 pins on the rear side of the eMMC have set functions as defined by the JEDEC specification. Some are used for supply voltage and ground for the core device and I/O commands, such as the V_SS, V_SSQ, V_CC, and V_CCQ as shown here. Some are also used as VSF or vendor specific functions, which are unique to Panasonic. These can be used to obtain card diagnostic info for current status or to do a failure analysis report.