IS66WVE4M16ALL
Advanced Information
Page Mode READ Operation
Page mode is a performance-enhancing extension to the legacy asynchronous READ
operation. In page-mode-capable products, an initial asynchronous read access is
preformed, then adjacent addresses can be read quickly by simply changing the low-
order address. Addresses A[3:0] are used to determine the members of the 16-address
PSRAM page. Any change in addresses A[4] or higher will initiate a new tAA access time.
Figure 4 shows the timing for a page mode access.
Page mode takes advantage of the fact that adjacent addresses can be read faster than
random addresses. WRITE operations do not include comparable page mode functionality.
The CE# LOW time is limited by refresh considerations. CE# must not stay LOW longer
than tCEM.
Figure 4. Page Mode READ Operation
Address
ADD0
ADD1
ADD2
ADD3
tAA
tAPA
tAPA
tAPA
DQ0-
DQ15
D0
D1
D2
D3
CE#
UB#/LB#
OE#
WE#
UB#/LB# Operation
The UB#/LB# enable signals accommodate byte-wide data transfers. During READ operations,
enabled bytes are driven onto the DQ. The DQ signals associated with a disabled byte are
put into a High-Z state during a READ operation. During WRITE operations, disabled bytes
are not transferred to the memory array. and the internal value remains unchanged. During
a WRITE cycle the data to be written is latched on the rising edge of CE#, WE#, LB# or UB#,
whichever occurs first.
When both the UB#/LB# are disabled (HIGH) during an operation, the device prevents the
data bus from receiving or transmitting data. Although the device may appear to be deselected,
it remains in active mode as long as CE# remains LOW.
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Rev.00C | March 2010
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
