A method of making a non-volatile MOS semiconductor memory device includes a formation step, in a semiconductor material substrate, of STI isolation regions filled by field oxide and of memory cells separated each other by said STI isolation regions. The devices comprise a head attached to a flexible element such as a gimbal. The method further comprises determining whether a second set of parameters is needed, the second set of parameters relating to said service and being valid when said service is controlled by a second network. The refresh cycle control circuit is capable of setting a 64-ms or 128-ms refresh cycle for the 64 subarrays and a 64-ms or 256-ms refresh cycle for 512 blocks. By utilizing this external box, the purpose of quickly easily removing the mass storage device is achieved.