CAT25M02_16 Datasheet, PDF (8/14 Pages) ON Semiconductor – 2 Mb SPI Serial CMOS EEPROM

CAT25M02
Byte Write
Once the WEL bit is set, the user may execute a write
sequence, by sending a WRITE instruction, a 24−bit address
and a data byte as shown in Figure 5. Only 18 significant
address bits are used by the CAT25M02. The rest are don’t
care bits, as shown in Table 10. Internal programming will
start after the low to high CS transition. During an internal
write cycle, all commands, except for RDSR (Read Status
Register) will be ignored. The RDY bit will indicate if the
internal write cycle is in progress (RDY high), or the device
is ready to accept commands (RDY low).
Page Write
After sending the first data byte to the CAT25M02, the
host may continue sending data, up to a total of 256 bytes,
according to timing shown in Figure 6. After each data byte,
the lower order address bits are automatically incremented,
while the higher order address bits (page address) remain
unchanged. If during this process the end of page is
exceeded, then loading will “roll over” to the first byte in the
page, thus possibly overwriting previoualy loaded data.
Table 10. BYTE ADDRESS
Device
Main Memory Array
Identification Page
Address Significant Bits
A17 − A0
A7 − A0
Following completion of the write cycle, the CAT25M02 is
automatically returned to the write disable state.
Write Identification Page
The additional 256-byte Identification Page (IP) can be
written with user data using the same Write commands
sequence as used for Page Write to the main memory array
(Figure 6). The IPL bit from the Status Register must be set
(IPL = 1) using the WRSR instruction, before attempting
to write to the IP. Prior to any write to the Identification
Page, the Write Enable Latch must be set (WEL=1) by
sending the WREN instruction.
The address bits [A23:A8] are Don’t Care and the
[A7:A0] bits define the byte address within the
Identification Page. In addition, the Byte Address must point
to a location outside the protected area defined by the BP1,
BP0 bits from the Status Register. When the full memory
array is write protected (BP1, BP0 = 1,1), the write
instruction to the IP is not accepted and not executed.
Also, the write to the IP is not accepted if the LIP bit from
the Status Register is set to 1 (the page is locked in Read-only
mode).
Address Don’t Care Bits
A23 – A18
A23 – A8
# Address Clock Pulses
24
24
CS
SCK
SI
012345678
29 30 31 32 33 34 35 36 37 38 39
OPCODE
BYTE ADDRESS*
DATA IN
0 0 0 0 0 0 1 0 AN
A₀ D7 D6 D5 D4 D3 D2 D1 D0
SO
HIGH IMPEDANCE
* Please check the Byte Address Table (Table 10)
Note: Dashed Line = mode (1, 1)
Figure 5. Byte WRITE Timing
CS
SCK
SI
012345678
29 30 31 32−39 40−47 32+(N−1)x8−1....32+(N−1)x8
32+Nx8−1
OPCODE
00 00 00
BYTEADDRESS*
DATA IN
1 0 A_N
A₀
Data Data
Byte 1 Byte 2
Data Byte N
7..1 0
HIGH IMPEDANCE
SO
* Please check the Byte Address Table (Table 10)
Note: Dashed Line = mode (1, 1)
Figure 6. Page WRITE Timing
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