9
AT25080A/160A/320A/640A
5082B–SEEPR–1/05
READ SEQUENCE (READ): Reading the AT25080A/160A/320A/640A via the serial
output (SO) pin requires the following sequence. After the CS
line is pulled low to select
a device, the read op-code is transmitted via the SI line followed by the byte address to
be read (A15−A0, see Table 10). Upon completion, any data on the SI line will be
ignored. The data (D7−D0) at the specified address is then shifted out onto the SO line.
If only one byte is to be read, the CS
line should be driven high after the data comes out.
The read sequence can be continued since the byte address is automatically incre-
mented and data will continue to be shifted out. When the highest address is reached,
the address counter will roll over to the lowest address, allowing the entire memory to be
read in one continuous read cycle.
WRITE SEQUENCE (WRITE): In order to program the AT25080A/160A/320A/640A,
two separate instructions must be executed. First, the device
must be write enabled
via
the WREN instruction. Then a Write (WRITE) instruction may be executed. Also, the
address of the memory location(s) to be programmed must be outside the protected
address field location selected by the block write protection level. During an internal
write cycle, all commands will be ignored except the RDSR instruction.
A Write instruction requires the following sequence. After the CS
line is pulled low to
select the device, the WRITE op-code is transmitted via the SI line followed by the byte
address (A15−A0) and the data (D7–D0) to be programmed (See Table 10). Program-
ming will start after the CS
pin is brought high. The low-to-high transition of the CS pin
must occur during the SCK low-time immediately after clocking in the D0 (LSB) data bit.
The READY/BUSY status of the device can be determined by initiating a read status
register (RDSR) instruction. If Bit 0 = “1”, the write cycle is still in progress. If Bit 0 = “0”,
the write cycle has ended. Only the RDSR instruction is enabled during the write pro-
gramming cycle.
The AT25080A/160A/320A/640A is capable of a 32-byte page write operation. After
each byte of data is received, the five low-order address bits are internally incremented
by one; the high-order bits of the address will remain constant. If more than 32 bytes of
data are transmitted, the address counter will roll over and the previously written data
will be overwritten. The AT25080A/160A/320A/640A is automatically returned to the
write disable state at the completion of a write cycle.
NOTE: If the device is not write enabled (WREN), the device will ignore the write instruc-
tion and will return to the standby state, when CS
is brought high. A new CS falling edge
is required to reinitiate the serial communication.
Table 10. Address Key
Address AT25080A AT25160A AT25320A AT25640A
A
N
A
9
–A
0
A
10
–A
0
A
11
–A
0
A
12
–A
0
Don’t
Care Bits
A
15
–A
10
A
15
–A
11
A
15
–A
12
A
15
–A
13
