EN25S40 Datasheet, PDF (6/37 Pages) Eon Silicon Solution Inc. – 4 Megabit 1.8V Serial Flash Memory with 4Kbyte Uniform Sector

OPERATING FEATURES
EN25S40
Standard SPI Modes
The EN25S40 is accessed through an SPI compatible bus consisting of four signals: Serial Clock (CLK),
Chip Select (CS#), Serial Data Input (DI) and Serial Data Output (DO). Both SPI bus operation Modes 0
(0,0) and 3 (1,1) are supported. The primary difference between Mode 0 and Mode 3, as shown in
Figure 3, concerns the normal state of the CLK signal when the SPI bus master is in standby and data
is not being transferred to the Serial Flash. For Mode 0 the CLK signal is normally low. For Mode 3 the
CLK signal is normally high. In either case data input on the DI pin is sampled on the rising edge of the
CLK. Data output on the DO pin is clocked out on the falling edge of CLK.
Figure 3. SPI Modes
Dual SPI Instruction
The EN25S40 supports Dual SPI operation when using the “ Dual Output Fast Read and Dual I/ O
FAST_READ “ (3Bh and BBh) instructions. These instructions allow data to be transferred to or from
the Serial Flash memory at two to three times the rate possible with the standard SPI. The Dual Read
instructions are ideal for quickly downloading code from Flash to RAM upon power-up (code-shadowing)
or for application that cache code-segments to RAM for execution. The Dual output feature simply
allows the SPI input pin to also serve as an output during this instruction. When using Dual SPI
instructions the DI and DO pins become bidirectional I/O pins; DQ₀ and DQ₁. All other operations use
the standard SPI interface with single output signal.
Page Programming
To program one data byte, two instructions are required: Write Enable (WREN), which is one byte, and
a Page Program (PP) sequence, which consists of four bytes plus data. This is followed by the internal
Program cycle (of duration t_PP).
To spread this overhead, the Page Program (PP) instruction allows up to 256 bytes to be programmed
at a time (changing bits from 1 to 0) provided that they lie in consecutive addresses on the same page
of memory.
Sector Erase, Block Erase and Chip Erase
The Page Program (PP) instruction allows bits to be reset from 1 to 0. Before this can be applied, the
bytes of memory need to have been erased to all 1s (FFh). This can be achieved a sector at a time,
using the Sector Erase (SE) instruction, a block at a time using the Block Erase (BE) instruction or
throughout the entire memory, using the Chip Erase (CE) instruction. This starts an internal Erase cycle
(of duration t_SE t_BE or t_CE). The Erase instruction must be preceded by a Write Enable (WREN)
instruction.
Polling During a Write, Program or Erase Cycle
A further improvement in the time to Write Status Register (WRSR), Program (PP) or Erase (SE, BE or
CE ) can be achieved by not waiting for the worst case delay (t_W, t_PP, t_SE, t_BE or t_CE). The Write In
Progress (WIP) bit is provided in the Status Register so that the application program can monitor its
value, polling it to establish when the previous Write cycle, Program cycle or Erase cycle is complete.
This Data Sheet may be revised by subsequent versions
6
or modifications due to changes in technical specifications.
©2004 Eon Silicon Solution, Inc.,
Rev. A, Issue Date: 2009/04/28
www.eonssi.com