at25df641a ATMEL Corporation, at25df641a Datasheet - Page 11

• Manufacturer Part Number: at25df641a
• Description: 64-mbit 2.7v Minimum Serial Peripheral Interface Serial Flash Memory
• Manufacturer: ATMEL Corporation

Figure 7-4.
8. Program and Erase Commands
8.1
8693A–DFLASH–8/10
SCK
SIO
SO
CS
Byte/Page Program
Dual-Output Read Array
HIGH-IMPEDANCE
MSB
0
0
0
1
1
2
OPCODE
Deasserting the CS pin will terminate the read operation and put the SO and SIO pins 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.
The Byte/Page Program command allows anywhere from a single byte of data to 256-bytes of
data to be programmed into previously erased memory locations. An erased memory location is
one that has all eight bits set to the logical “1” state (a byte value of FFh). Before a Byte/Page
Program command can be started, the Write Enable command must have been previously
issued to the device (see
the Status Register to a logical “1” state.
To perform a Byte/Page Program command, an opcode of 02h must be clocked into the device
followed by the three address bytes denoting the first byte location of the memory array to begin
programming at. After the address bytes have been clocked in, data can then be clocked into the
device and will be stored in an internal buffer.
If the starting memory address denoted by A23-A0 does not fall on an even 256-byte page
boundary (A7-A0 are not all 0), then special circumstances regarding which memory locations to
be programmed will apply. In this situation, any data that is sent to the device that goes beyond
the end of the page will wrap around back to the beginning of the same page. For example, if the
starting address denoted by A23-A0 is 0000FEh, and three bytes of data are sent to the device,
then the first two bytes of data will be programmed at addresses 0000FEh and 0000FFh while
the last byte of data will be programmed at address 000000h. The remaining bytes in the page
(addresses 000001h through 0000FDh) will not be programmed and will remain in the erased
state (FFh). In addition, if more than 256-bytes of data are sent to the device, then only the last
256 bytes sent will be latched into the internal buffer.
When the CS pin is deasserted, the device will take the data stored in the internal buffer and pro-
gram it into the appropriate memory array locations based on the starting address specified by
A23-A0 and the number of data bytes sent to the device. If less than 256-bytes of data were sent
to the device, then the remaining bytes within the page will not be programmed and will remain
in the erased state (FFh). The programming of the data bytes is internally self-timed and should
take place in a time of t
1
3
1
4
0
5
1
6
1
7
MSB
A
8
A
9
ADDRESS BITS A23-A0
A
10 11
A
PP
A
12
“Write Enable” on page
A
or t
BP
if only programming a single byte.
Atmel AT25DF641A [Preliminary]
A
29 30
A
A
31 32
MSB
X
X
33
DON'T CARE
X
34
X
35
20) to set the Write Enable Latch (WEL) bit of
X
36
X
37 38
X
X
39
MSB
D 6
D 7
DATA BYTE 1
40
OUTPUT
D 4
D 5
41
D 2
D 3
42 43
D 0
D 1
MSB
D 6
D 7
DATA BYTE 2
44
OUTPUT
D 4
D 5
45
D 2
D 3
46
D 0
D 1
47 48
MSB
D 6
D 7
D 4
D 5
11