CAT25C03 Datasheet, PDF (6/10 Pages) Catalyst Semiconductor – 2K/4K/8K/16K/32K SPI Serial CMOS E2PROM

CAT25C03/05/09/17/33
Advanced
DEVICE OPERATION
Write Enable and Disable
The CAT25C03/05/09/17/33 contains a write enable
latch. This latch must be set before any write operation.
The device powers up in a write disable state when Vcc
is applied. WREN instruction will enable writes (set the
latch) to the device. WRDI instruction will disable writes
(reset the latch) to the device. Disabling writes will
protect the device against inadvertent writes.
READ Sequence
The part is selected by pulling CS low. The 8-bit read
instruction is transmitted to the CAT25C03/05/09/17/33,
followed by the 16-bit address for 25C09/17/33 (only 10-
bit addresses are used for 25C09, 11-bit addresses are
used for 25C17, and 12-bit addresses are used for
25C33. The rest of the bits are don't care bits) and 8-bit
address for 25C03/05 (for the 25C05, bit 3 of the read
data instruction contains address A8).
After the correct read instruction and address are sent,
the data stored in the memory at the selected address is
shifted out on the SO pin. The data stored in the memory
at the next address can be read sequentially by continu-
ing to provide clock pulses. The internal address pointer
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
0000h allowing the read cycle to be continued indefi-
nitely. The read operation is terminated by pulling the CS
high. Read sequece is illustrated in Figure 4. Reading
status register is illustrated in Figure 5. To read the status
register, RDSR instruction should be sent. The contents
of the status register are shifted out on the SO line. If a
non-volatile write is in progress, the RDSR instruction
returns a high on SO. When the non-volatile write cycle
is completed, the status register data is read out.
Figure 2. WREN Instruction Timing
SK
CS
SI
00000 1 1 0
HIGH-Z
SO
Figure 3. WRDI Instruction Timing
SK
CS
SI
0 0 0 0 0 1 00
HIGH-Z
SO
25C128 F05
Doc. No. 25068-00 2/98
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