Today removable memory planet will talk about solid-state storage is a very popular type of removable memory for small devices is flash memory. Flash memory is a type of solid-state technology, which means that there are no moving parts. Inside the chip in the flash memory is a grid of columns and rows, with a two transistor cell at each intersecting point on the grid. The two transistors are separated by a thin oxide layer. One of the transistors is called the floating gate, and the other one is the control gate. The floating gate's link to the row is through the control gate. As long as this link is in place, the cell has a value of "1".
To change the cell value to a "0" requires a process called Fowler-Nordheim tunneling. Tunneling is used to alter the placement of electrons in the floating gate. An electrical charge, usually between 10 and 13 volts, is applied to the floating gate. The charge comes from the column, or bit line, enters the floating gate and drains to a ground.
This charge causes the floating-gate transistor to act like an electron gun. The excited, negatively charged electrons are pushed through and trapped on the other side of the oxide layer, which acquires a negative charge. The electrons act as a barrier between the control gate and the floating gate. A device called a cell sensor monitors the level of the charge passing through the floating gate. If the flow through the gate is greater than fiffty percent of the charge, it has a value of "1". If the charge passing through drops below the fifty-percent of the threshold, the value changes to "0".
No comments:
Post a Comment