at25df321a ATMEL Corporation, at25df321a Datasheet - Page 31

• Manufacturer Part Number: at25df321a
• Description: 32-megabit 2.7-volt Minimum Spi Serial Flash Memory
• Manufacturer: ATMEL Corporation

10.3
Figure 10-3. Read Sector Lockdown Register
3686C–DFLASH–12/08
SCK
SO
CS
SI
Read Sector Lockdown Registers
HIGH-IMPEDANCE
MSB
0
0
0
1
1
2
OPCODE
Figure 10-2. Freeze Sector Lockdown State
The Sector Lockdown Registers can be read to determine the current lockdown status of each
physical 64-Kbyte sector. To read the Sector Lockdown Register for a particular 64-Kbyte sec-
tor, the CS pin must first be asserted and the opcode of 35h must be clocked in. Once the
opcode has been clocked in, three address bytes designating any address within the 64-Kbyte
sector must be clocked in. After the address bytes have been clocked in, data will be output 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 Lockdown Register.
At clock frequencies above f
ing at clock frequencies above f
device in order to determine the correct status of the appropriate Sector Lockdown Register.
Table 10-2.
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.
1
3
Output Data
0
4
SCK
1
5
FFh
00h
SO
CS
SI
0
6
1
7
MSB
A
8
Read Sector Lockdown Register – Output Data
A
9
ADDRESS BITS A23-A0
Sector Lockdown Register Value
Sector Lockdown Register value is 0 (sector is not locked down).
Sector Lockdown Register value is 1 (sector is permanently locked down).
A
10 11
MSB
HIGH-IMPEDANCE
A
0
0
A
12
0
1
A
1
2
OPCODE
CLK
1
3
, the first byte of data output will not be valid. Therefore, if operat-
0
4
A
29 30
CLK
1
5
A
, at least two bytes of data must be clocked out from the
0
6
A
31 32
0
MSB
7
X
MSB
ADDRESS BITS A23-A0
0
8
X
33
1
AT25DF321A [Preliminary]
DON'T CARE
9
X
34
0
X
35
X
36
X
37 38
0
29 30
X
0
X
39
0
31 32
MSB
MSB
D
40
CONFIRMATION BYTE IN
1
D
41
1
33
DATA BYTE
D
42 43
0
34
D
1
35
D
44
0
36
D
45
0
37 38
D
46
0
D
47 48
0
39
MSB
D
D
31