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
