Mated Film Storage Read/Write Cycle

Fire Controlman Volume 03-Digital Data Systems
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Mated Film Storage Read/Write Cycle Similar to core memory, mated film memory must restore data back into memory after it has been read from memory so it will not be lost. READ CYCLE. —To read a mated film memory cell, a current is generated along the word line and a transverse field is applied to the thin film cell. The rotation of the magnetic vector when it aligns with the word line, causes a current in the sense/digit line. This resulting current in the sense/digit line is read as a binary zero or one by the register at the end of the sense/digit line. This mechanism is graphically shown in frame A of figure 6-22. The mated film memory cell in frame B of figure 6-22 is in the zero magnetic state. When the word field is applied, the magnetic polarization vector is rotated 90° to the hard direction. The clockwise direction of flux change induces a small voltage generating current in the sense/digit line as shown. The thin film in frame C of figure 6-22 is in the one state. The transverse field is applied by driving a pulse down the word line and the vector is forced in the hard direction, but now the flux change is counterclockwise. This flux change alSO induces a small voltage generating current in the sense/digit line, but it is the opposite polarity of the signal read from the film, thus storing a zero. Figure 6-22.—Reading a zero or a one: A. The mechanism; B. Zero state; C. One state. 6-18

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