X25F087 Datasheet, PDF (3/13 Pages) Xicor Inc. – SPI SerialFlash with Block Lock TM Protection

X25F087
Figure 1. Status Register/Block Lock Protection Byte
76543210
0 0 0 0 0 BL2 BL1 BL0
Note: Bits [7:3] specified to be “0’s”
7007 FRM T02
Read Sequence
When reading from the SerialFlash memory array, CS is
first pulled LOW to select the device. The 8-bit READ
instruction is transmitted to the X25F087, followed by the
16-bit address, of which the last 10 bits are used (bits
[15:10] specified to be "0’s"). After the READ opcode and
address are sent, the data stored in the memory at the
selected address is shifted out on the SO line. The data
stored in memory at the next address can be read
sequentially by continuing to provide clock pulses. The
address is automatically incremented to the next higher
address after each byte of data is shifted out. When the
highest address is reached (03FFh), the address counter
rolls over to address 0000h, allowing the read cycle to be
continued indefinitely. The read operation is terminated
by taking CS HIGH (Figure 2).
Sector Program Sequence
Prior to any attempt to program data into the X25F087,
the “Program Enable” latch must first be set by issuing
the PREN instruction (Table 1 and Figure 4). CS is first
taken LOW. Then the PREN instruction is clocked into
the X25F087. After all eight bits of the instruction are
transmitted, CS must then be taken HIGH. If the user
continues the program operation without taking CS HIGH
after issuing the PREN instruction, the program opera-
tion will be ignored.
To program data to the SerialFlash memory array, the
user then issues the PROGRAM instruction, followed by
the 16 bit address of the first location in the sector and
then the 16 bytes of data to be programmed. Only the last
9 bits of the address are used and bits [15:9] are speci-
fied to be "0’s". The entire write operation takes 152
clocks. CS must go LOW and remain LOW for the dura-
tion of the operation. The host must program 16 bytes in
each write with the restriction that these bytes reside on
one sector. If the address counter reaches the end of the
sector and the clock continues, or if fewer than 16 bytes
are clocked in, the contents of the sector cannot be guar-
anteed.
For a sector program operation to be completed, CS can
only be brought HIGH after bit 0 of the last data byte to
be programmed is clocked in. If it is brought HIGH at any
other time, the program operation will not be completed.
(Figure 5)
Read Status Operation
If there is not a nonvolatile write in progress, the Read
Status instruction returns the Block Lock Protection byte
from the Status Register which contains the Block Lock
Protection bits BL2-BL0 (Figure 1). The Block Lock Pro-
tection bits define the Block Lock Protection condition
(Figure 1 and Table1). The other bits are reserved and
will return "0’s" when read (Figure 3).
If a nonvolatile write is in progress, the Read Status
instruction returns the status of the internal write opera-
tion on SO. When the nonvolatile write cycle is com-
pleted, the status register data is again read out.
During a nonvolatile write in progress, the SO pin will be
set HIGH. At the end of the nonvolatile write cycle, SO is
set to output the current bit from the status register.
Clocking SCK is valid during a nonvolatile write in
progress, but is not necessary. If the SCK line is clocked,
the pointer to the status register is also clocked, even
though the SO pin shows the status of the nonvolatile
write operation (Figure 3). When the pointer reaches the
end of the eight bit status register, it “rolls over” to the first
bit of the register.
Program Status Operation
Prior to any attempt to perform a Program Status Opera-
tion, the PREN instruction must first be issued. This
instruction sets the “Program Enable” latch and allows
the part to respond to a Program Status sequence (Fig-
ure 6). The Program Status instruction follows and con-
sists of one command byte followed by one Block Lock
Protection byte (Figure 1). This byte contains the Block
Lock Protection bits BL2-BL0. The rest of the bits [7:3]
are unused and must be programmed as “0’s”. Bringing
CS HIGH after the two byte Program Status instruction
initiates a nonvolatile write to the Status Register. Pro-
gramming more than one byte to the Status Register will
overwrite the previously programmed Block Lock Protec-
tion byte (Table 1).
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