Program and erase commands, 1 byte/page program – Rainbow Electronics AT25DQ161 User Manual
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AT25DQ161 [DATASHEET]
8671C–DFLASH–11/2012
8.
Program and Erase Commands
8.1
Byte/Page Program
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
) to set the Write Enable Latch (WEL) bit of 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.
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 is 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 program 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
PP
or t
BP
if only programming a single byte.
The three address bytes and at least one complete byte of data must be clocked into the device before the CS pin is
deasserted, and the CS pin must be deasserted on even byte boundaries (multiples of eight bits); otherwise, the device
will abort the operation and no data will be programmed into the memory array. In addition, if the address specified by
A23-A0 points to a memory location within a sector that is in the protected state (see
locked down (see
), then the Byte/Page Program command will not be executed, and the
device will return to the idle state once the CS pin has been deasserted. The WEL bit in the Status Register will be reset
back to the Logical 0 state if the program cycle aborts due to an incomplete address being sent, an incomplete byte of
data being sent, the CS pin being deasserted on uneven byte boundaries, or because the memory location to be
programmed is protected or locked down.
While the device is programming, the Status Register can be read and will indicate that the device is busy. For faster
throughput, it is recommended that the Status Register be polled rather than waiting the t
BP
or t
PP
time to determine if the
data bytes have finished programming. At some point before the program cycle completes, the WEL bit in the Status
Register will be reset back to the Logical 0 state.
The device also incorporates an intelligent programming algorithm that can detect when a byte location fails to program
properly. If a programming error arises, it will be indicated by the EPE bit in the Status Register.