M58WR064 STMICROELECTRONICS [STMicroelectronics], M58WR064 Datasheet - Page 30

• Manufacturer Part Number: M58WR064
• Description: 64 Mbit 4Mb x 16, Multiple Bank, Burst 1.8V Supply Flash Memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M58WR064ET, M58WR064EB
READ MODES
Read operations can be performed in two different
ways depending on the settings in the Configura-
tion Register. If the clock signal is ‘don’t care’ for
the data output, the read operation is Asynchro-
nous; if the data output is synchronized with clock,
the read operation is Synchronous.
The Read mode and data output format are deter-
mined by the Configuration Register. (See Config-
uration Register section for details). All banks
supports both asynchronous and synchronous
read operations. The Multiple Bank architecture
allows read operations in one bank, while write op-
erations are being executed in another (see Ta-
bles 11 and 12).
Asynchronous Read Mode
In Asynchronous Read operations the clock signal
is ‘don’t care’. The device outputs the data corre-
sponding to the address latched, that is the mem-
ory array, Status Register, Common Flash
Interface or Electronic Signature depending on the
command issued. CR15 in the Configuration Reg-
ister must be set to ‘1’ for Asynchronous opera-
tions.
In Asynchronous Read mode a Page of data is in-
ternally read and stored in a Page Buffer. The
Page has a size of 4 Words and is addressed by
A0 and A1 address inputs. The address inputs A0
and A1 are not gated by Latch Enable in Asyn-
chronous Read mode.
The first read operation within the Page has a
longer access time (T
subsequent reads within the same Page have
much shorter access times. If the Page changes
then the normal, longer timings apply again.
Asynchronous Read operations can be performed
in two different ways, Asynchronous Random Ac-
cess Read and Asynchronous Page Read. Only
Asynchronous Page Read takes full advantage of
the internal page storage so different timings are
applied.
During Asynchronous Read operations, after a
bus inactivity of 150ns, the device automatically
switches to the Automatic Standby mode. In this
condition the power consumption is reduced to the
standby value and the outputs are still driven.
In Asynchronous Read mode, the WAIT signal is
always asserted.
See Table 20, Asynchronous Read AC Character-
istics, Figure 10, Asynchronous Random Access
Read AC Waveform and Figure 11, Asynchronous
Page Read AC Waveform for details.
Synchronous Burst Read Mode
In Synchronous Burst Read mode the data is out-
put in bursts synchronized with the clock. It is pos-
30/82
acc
, Random access time),
sible to perform burst reads across bank
boundaries.
Synchronous Burst Read mode can only be used
to read the memory array. For other read opera-
tions, such as Read Status Register, Read CFI
and Read Electronic Signature, Single Synchro-
nous Read or Asynchronous Random Access
Read must be used.
In Synchronous Burst Read mode the flow of the
data output depends on parameters that are con-
figured in the Configuration Register.
A burst sequence is started at the first clock edge
(rising or falling depending on Valid Clock Edge bit
CR6 in the Configuration Register) after the falling
edge of Latch Enable or Chip Enable, whichever
occurs last. Addresses are internally incremented
and after a delay of 2 to 5 clock cycles (X latency
bits CR13-CR11) the corresponding data are out-
put on each clock cycle.
The number of Words to be output during a Syn-
chronous Burst Read operation can be configured
as 4 or 8 Words or Continuous (Burst Length bits
CR2-CR0). The data can be configured to remain
valid for one or two clock cycles (Data Output Con-
figuration bit CR9).
The order of the data output can be modified
through the Burst Type and the Wrap Burst bits in
the Configuration Register. The burst sequence
may be configured to be sequential or interleaved
(CR7). The burst reads can be confined inside the
4 or 8 Word boundary (Wrap) or overcome the
boundary (No Wrap). If the starting address is
aligned to the Burst Length (4 or 8 Words), the
wrapped configuration has no impact on the output
sequence. Interleaved mode is not allowed in Con-
tinuous Burst Read mode or with No Wrap se-
quences.
A WAIT signal may be asserted to indicate to the
system that an output delay will occur. This delay
will depend on the starting address of the burst se-
quence; the worst case delay will occur when the
sequence is crossing a 64 word boundary and the
starting address was at the end of a four word
boundary.
WAIT is asserted during X latency, the Wait state
and at the end of 4- and 8-Word burst. It is only
deasserted when output data are valid. In Contin-
uous Burst Read mode a Wait state will occur
when crossing the first 64 Word boundary. If the
burst starting address is aligned to a 4 Word Page,
the Wait state will not occur.
The WAIT signal can be configured to be active
Low or active High (default) by setting CR10 in the
Configuration Register. The WAIT signal is mean-
ingful only in Synchronous Burst Read mode, in