W28V400B/T
3. PRODUCT OVERVIEW
The W28V400B/T is a high-performance 4M-bit SmartVoltage Flash memory organized as 512k-byte
of 8 bits or 256k-word of 16 bits. The 512k-byte/256k-word of data is arranged in two 8k-byte/4k-word
boot blocks, six 8k-byte/4k-word parameter blocks and seven 64kbyte/32k-word main blocks which
are individually erasable in-system. The memory map is shown in Figure 3.
SmartVoltage technology provides a choice of VDD and VPP combinations, as shown in Table 1, to
meet system performance and power expectations. 2.7V VDD consumes approximately one-fifth the
power of 5V VDD. But, 5V VDD provides the highest read performance. VPP at 2.7, 3.3V and 5V
eliminates the need for a separate 12V converter, while VPP = 12V maximizes block erase and
word/byte write performance. In addition to flexible erase and program voltages, the dedicated VPP pin
gives complete data protection when VPP ≤ VPPLK
.
Table 1. VDD and VPP Voltage Combinations Offered by SmartVoltage Technology
VDD VOLTAGE
VPP VOLTAGE
2.7V, 3.3V, 5V, 12V
3.3V, 5V, 12V
5V, 12V
2.7V
3.3V
5V
Internal VDD and VPP detection Circuitry automatically configures the device for optimized read and
write operations.
A Command User Interface (CUI) serves as the interface between the system processor and internal
operation of the device. A valid command sequence written to the CUI initiates device automation. An
internal Write State Machine (WSM) automatically executes the algorithms and timings necessary for
block erase and word/byte write operations.
A block erase operation erases one of the device’s 32k-word blocks typically within 0.39s (5V VDD,
12V VPP), 4k-word blocks typically within 0.25s (5V VDD, 12V VPP) independent of other blocks. Each
block can be independently erased 100,000 times. Block erase suspend mode allows system software
to suspend block erase to read or write data from any other block.
Writing memory data is performed in word/byte increments of the device’s 32k-word blocks typically
within 8.4 µS (5V VDD, 12V VPP), 4k-word blocks typically within 17 µS (5V VDD, 12V VPP). Word/byte
write suspend mode enables the system to read data or execute code from any other flash memory
array location.
The boot blocks can be locked for the #WP pin. Block erase or word/byte write for boot block must not
be carried out by #WP to Low and #RESET to VIH.
The status register indicates when the WSM’s block erase or word/byte write operation is finished.
The RY/#BY output gives an additional indicator of WSM activity by providing both a hardware signal
of status (versus software polling) and status masking (interrupt masking for background block erase,
for example). Status polling using RY/#BY minimizes both CPU overhead and system power
consumption. When low, RY/#BY indicates that the WSM is performing a block erase or word/byte
write. RY/#BY-high indicates that the WSM is ready for a new command, block erase is suspended
(and word/byte write is inactive), word/byte write is suspended, or the device is in deep power-down
mode.
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