M69AW048BL70ZB8 Просмотр технического описания (PDF) - STMicroelectronics
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M69AW048BL70ZB8 Datasheet PDF : 29 Pages
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M69AW048B
OPERATION
Operational modes are determined by device con-
trol inputs W, E1, E2, LB and UB as summarized
in the Operating Modes table (see Table
2., Operating Modes).
Power-Up Sequence
Because the internal control logic of the
M69AW048B needs to be initialized, the following
Power-Up procedure must be followed before the
memory is used:
– Apply power and wait for VCC to stabilize,
– Wait 300µs while driving both Chip Enable
signals (E1 and E2) High.
See also Figure 24. for details on the Power-Up
AC waveforms.
Read Mode
The device is in Read mode when:
– Write Enable (W) is High and
– Output Enable (G) Low and
– the two Chip Enable signals are asserted
(E1 is Low, and E2 is High).
The time taken to enter Read mode (tELQV, tGLQV
or tBLQV) depends on which of the above signals
was the last to reach the appropriate level.
Data out (DQ15-DQ0) may be indeterminate dur-
ing tELQX, tGLQX and tBLQX but data will always be
valid during tAVQV. See Figures 7, 8, 9, 10 and 11
and Table 11., Read Mode AC Characteristics, for
details of when the outputs become valid.
Write Mode
The device is in Write mode when
– Write Enable (W) is Low and
– Chip Enable (E1) is Low and E2 is High
– at least one of Upper Byte Enable (UB)
and Lower Byte Enable (LB) is Low.
The Write cycle begins just after the event (the fall-
ing edge) that causes the last of these conditions
to become true (tAVWL or tAVEL or tAVBL).
The Write cycle is terminated by the rising edge of
Write Enable (W) or Chip Enable (E1), whichever
occurs first.
If the device is in Write mode (Chip Enable (E1) is
Low, Output Enable (G) is Low, Upper Byte En-
able (UB) and/or Lower Byte Enable (LB) is Low,
then Write Enable (W) will return the outputs to
high impedance within tWHDZ of its rising edge.
Care must be taken to avoid bus contention in this
type of operation. Data input must be valid for tD-
VWH before the rising edge of Write Enable (W), or
for tDVEH before the rising edge of Chip Enable
(E1), whichever occurs first, and remain valid for
tBHDZ, tWHDZ, tEHDZ.
See Figures 12, 13, 14, 15, 16 and 17 and Table
12., Write Mode AC Characteristics, for details of
when the outputs become valid.
Standby Mode
The device is in Standby mode when:
– Chip Enable (E1) is High and
– Chip Enable (E2) is High
The input/output buffers and the decoding/control
logic are switched off, but the dynamic array con-
tinues to be refreshed. In this mode, the memory
current consumption, ISB, is reduced, and the data
remains valid.
See Figures 17 and Table 13., Standby/Power-
Down Mode AC Characteristics, for details of
when the outputs become valid.
Power-down Modes
Description of Power-Down Modes. The
M69AW048B has four Power-down modes, Deep
Power-Down, 4 Mbit Partial Array Refresh, 8 Mbit
Partial Array Refresh, and 16 Mbit Partial Array
Refresh (see Table 4. and Figure 22.).
These can be entered using a series of read and
write operations. Each mode has following fea-
tures. The default state is Deep Power-Down and
it is the lowest power consumption but all data will
be lost once E2 is brought Low for Power-down.
No sequence is required to put the device in Deep
Power-Down mode after Power-up.
The device is in one of the Power-down modes
when:
– Chip Enable (E2) is Low
All the device logic is switched off and all internal
operations are suspended. This gives the lowest
power consumption. In this operating mode, no re-
fresh is performed, and data is lost if the duration
is longer than 10ns. This mode is useful for those
applications where the data contents are no longer
needed, and can be lost, but where reduced cur-
rent consumption is of major importance.
Power-Down Program Sequence. The Power-
Down Program sequence is used to program the
Power-Down Configuration. It requires a total of
six read and write operations, with specific ad-
dresses and data. Between each read or write op-
eration the device must be in Standby mode.
Table 4. shows the sequence. In the first cycle, the
Byte at the highest memory address (MSB) is read.
In the second and third cycles, the data (RDa) read
by first cycle are written back. If the third cycle is
written into a different address, the sequence is
aborted, and the data written by the third cycle is
valid as in a normal write operation. In the fourth
and fifth cycles, the Power-Down Configuration
data is written. The data of the fourth cycle must be
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