AT26F004-SSU ATMEL [ATMEL Corporation], AT26F004-SSU Datasheet - Page 17

• Manufacturer Part Number: AT26F004-SSU
• Description: 4-megabit 2.7-volt Only Serial Firmware DataFlash Memory
• Manufacturer: ATMEL [ATMEL Corporation]

9.5
3588A–DFLSH–10/05
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.
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
Figure 9-5.
SCK
Output Data
SO
CS
SI
FFh
00h
Read Sector Protection Register – Output Data
Read Sector Protection Register
MSB
HIGH-IMPEDANCE
Sector Protection Register Value
Sector Protection Register value is 0 (sector is unprotected).
Sector Protection Register value is 1 (sector is protected).
0
0
0
1
1
2
OPCODE
1
3
“Status Register Commands” on page 19
1
4
1
5
0
6
0
7
MSB
A
8
A
9
ADDRESS BITS A23-A0
A
10 11
A
A
12
A
A
29 30
A
A
31 32
MSB
D
D
33
for more details).
DATA BYTE
D
34
D
35
D
36
D
AT26F004
37 38
D
D
39 40
MSB
D
D
17