X5328/X5329
Characteristics subject to change without notice.
7 of 21
REV 1.1.1 3/6/01
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Read Sequence
When reading from the EEPROM memory array, CS is
first pulled low to select the device. The 8-bit READ
instruction is transmitted to the device, followed by the
16-bit address. 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 sequen-
tially 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, the address counter rolls
over to address $0000 allowing the read cycle to be
continued indefinitely. The read operation is terminated
by taking CS high. Refer to the Read EEPROM Array
Sequence (Figure 1).
To read the Status Register, the CS line is first pulled low
to select the device followed by the 8-bit RDSR instruc-
tion. After the RDSR opcode is sent, the contents of the
Status Register are shifted out on the SO line. Refer to
the Read Status Register Sequence (Figure 2).
Write Sequence
Prior to any attempt to write data into the device, the
“Write Enable” Latch (WEL) must first be set by issuing
the WREN instruction (Figure 3). CS is first taken LOW,
then the WREN instruction is clocked into the device.
After all eight bits of the instruction are transmitted, CS
must then be taken HIGH. If the user continues the
Write Operation without taking CS HIGH after issuing
the WREN instruction, the Write Operation will be
ignored.
To write data to the EEPROM memory array, the user
then issues the WRITE instruction followed by the
16-bit address and then the data to be written. Any
unused address bits are specified to be “0’s”. The
WRITE operation minimally takes 32 clocks. CS must
go low and remain low for the duration of the operation.
If the address counter reaches the end of a page and
the clock continues, the counter will roll back to the first
address of the page and overwrite any data that may
have been previously written.
For the Page Write Operation (byte or page write) to be
completed, CS can only be brought HIGH after bit 0 of
the last data byte to be written is clocked in. If it is
brought HIGH at any other time, the write operation will
not be completed (Figure 4).
To write to the Status Register, the WRSR instruction is
followed by the data to be written (Figure 5). Data bits 0
and 1 must be “0”.
While the write is in progress following a Status Register
or EEPROM Sequence, the Status Register may be
read to check the WIP bit. During this time the WIP bit
will be high.
OPERATIONAL NOTES
The device powers-up in the following state:
– The device is in the low power standby state.
– A HIGH to LOW transition on CS is required to enter
an active state and receive an instruction.
– SO pin is high impedance.
– The Write Enable Latch is reset.
– The Flag Bit is reset.
– Reset Signal is active for t
PURST
.
Data Protection
The following circuitry has been included to prevent
inadvertent writes:
– A WREN instruction must be issued to set the Write
Enable Latch.
– CS must come HIGH at the proper clock count in
order to start a nonvolatile write cycle.