AT26F004 Datasheet, PDF (17/37 Pages) ATMEL Corporation – 4-megabit 2.7-volt Only Serial Firmware DataFlash Memory

AT26F004
9.5 Read Sector Protection Registers
The Sector Protection Registers can be read to determine the current software protection status
of each sector. Reading the Sector Protection Registers, however, will not determine the status
of the WP pin.
To read the Sector Protection Register for a particular sector, the CS pin must first be asserted
and the opcode of 3Ch must be clocked in. Once the opcode has been clocked in, three address
bytes designating any address within the sector must be clocked in. After the last address byte
has been clocked in, the device will begin outputting data on the SO pin during every subse-
quent clock cycle. The data being output will be a repeating byte of either FFh or 00h to denote
the value of the appropriate Sector Protection Register.
Table 9-2. Read Sector Protection Register – Output Data
Output Data Sector Protection Register Value
00h
Sector Protection Register value is 0 (sector is unprotected).
FFh
Sector Protection Register value is 1 (sector is protected).
Deasserting the CS pin will terminate the read operation and put the SO pin into a high-imped-
ance state. The CS pin can be deasserted at any time and does not require that a full byte of
data be read.
In addition to reading the individual Sector Protection Registers, the Software Protection Status
(SWP) bit in the Status Register can be read to determine if all, some, or none of the sectors are
software protected (refer “Status Register Commands” on page 19 for more details).
Figure 9-5. Read Sector Protection Register
CS
SCK
SI
SO
0 1 2 3 4 5 6 7 8 9 10 11 12
29 30 31 32 33 34 35 36 37 38 39 40
OPCODE
ADDRESS BITS A23-A0
0 0 1 1 1 1 0 0AAAAAA
MSB
MSB
HIGH-IMPEDANCE
AAA
DATA BYTE
DDDDDDDDDD
MSB
MSB
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