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M27C160 Device description
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When in the standby mode, the outputs are in a high impedance state, independent of the G
input.
2.3 Two-line output control
Because EPROMs are usually used in larger memory arrays, this product features a 2-line
control function which accommodates the use of multiple memory connection. The two line
control function allows:
● the lowest possible memory power dissipation,
● complete assurance that output bus contention will not occur.
For the most efficient use of these two control lines, E
should be decoded and used as the
primary device selecting function, while G
should be made a common connection to all
devices in the array and connected to the READ
line from the system control bus. This
ensures that all deselected memory devices are in their low power standby mode and that
the output pins are only active when data is required from a particular memory device.
2.4 System considerations
The power switching characteristics of Advanced CMOS EPROMs require careful
decoupling of the supplies to the devices. The supply current I
CC
has three segments of
importance to the system designer: the standby current, the active current and the transient
peaks that are produced by the falling and rising edges of E
.
The magnitude of the transient current peaks is dependent on the capacitive and inductive
loading of the device outputs. The associated transient voltage peaks can be suppressed by
complying with the two line output control and by properly selected decoupling capacitors. It
is recommended that a 0.1µF ceramic capacitor is used on every device between V
CC
and
V
SS
. This should be a high frequency type of low inherent inductance and should be placed
as close as possible to the device. In addition, a 4.7µF electrolytic capacitor should be used
between V
CC
and V
SS
for every eight devices.
This capacitor should be mounted near the power supply connection point. The purpose of
this capacitor is to overcome the voltage drop caused by the inductive effects of PCB traces.
2.5 Programming
When delivered (and after each erasure for UV EPROM), all bits of the M27C160 are in the
'1' state. Data is introduced by selectively programming '0's into the desired bit locations.
Although only '0's will be programmed, both '1's and '0's can be present in the data word.
The only way to change a '0' to a '1' is by die exposure to ultraviolet light (UV EPROM). The
M27C160 is in the programming mode when V
PP
input is at 12.5V, G is at V
IH
and E is
pulsed to V
IL
. The data to be programmed is applied to 16 bits in parallel to the data output
pins. The levels required for the address and data inputs are TTL. V
CC
is specified to be
6.25V ± 0.25V.
2.6 Presto III programming algorithm
The Presto III Programming Algorithm allows the whole array to be programed with a
guaranteed margin in a typical time of 52.5 seconds. Programming with Presto III consists of
