User guide

23
8715C–SFLSH–11/2012
AT25DF081A
9.6 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 output-
ting data on the SO pin during every subsequent 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.
At clock frequencies above f
CLK
, the first byte of data output will not be valid. Therefore, if operating at clock fre-
quencies above f
CLK
, at least two bytes of data must be clocked out from the device in order to determine the
correct status of the appropriate Sector Protection Register.
Deasserting the CS pin will terminate the read operation and put the SO pin into a high-impedance 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) bits in the
Status Register can be read to determine if all, some, or none of the sectors are software protected (refer to “Read
Status Register” on page 31 for more details).
Figure 9-5. Read Sector Protection Register
Table 9-3. 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)
SCK
CS
SI
SO
MSB MSB
2310
00111100
675410119812 373833 36353431 3229 30 39 40
OPCODE
AAAA AAAA A
MSB MSB
DDDDDDDDDD
ADDRESS BITS A23-A0
DATA BYTE
HIGH-IMPEDANCE