TF4 Technical Information
to the memory device. If the data on the bus is not inverted this power control signal
(PS), is at logic "0" state. If the data that is presented on the bus is inverted, this is indi-
cated by PS = logic "1". This PS signal is a common signal for all the devices connected to
the address/memory bus. The transmitting device uses the PS signal to indicate non-
inverted or inverted data. As only one device at a time, can present data on the address/
data bus, this signal is shared and only one additional control signal PS is needed for the
address/data bus, although the data bus may be connected to several devices. The below
figure shows how this PS-signal actually works.
The data is compared by using an XOR-function. The result can be seen above. In Figure
12 there is more equal bits than unequal bits, so therefor the data is not inverted before
it is sent out to the flash. This means that the PS-signal is "0". The next scenario shows
the opposite situation.
The comparison shows more unequal bits than equal bits, and the bits are inverted on
Figure 12: Truth Table for PS=0
Figure 13: Truth Table for PS=1
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Issue 2.0 Mar/2005