X24641S8-1.8 XICOR [Xicor Inc.], X24641S8-1.8 Datasheet - Page 8
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X24641S8-1.8
Manufacturer Part Number
X24641S8-1.8
Description
400 KHz 2-Wire Serial E 2 PROM
Manufacturer
XICOR [Xicor Inc.]
Datasheet
1.X24641S8-1.8.pdf
(13 pages)
Random Read
Random read operation allows the master to access
any memory location in the array. Prior to issuing the
Slave Address Byte with the R/W bit set to one, the
master must first perform a “Dummy” write operation.
The master issues the start condition and the Slave
Address Byte with the R/W bit low, receives an
acknowledge, then issues Address Byte 1, receives
another acknowledge, then issues Address Byte 0
containing the address of the byte to be read. After the
device acknowledges receipt of Address Byte 0, the
master issues another start condition and the Slave
Address Byte with the R/W bit set to one. This is
followed by an acknowledge and then eight bits of data
from the device. The master terminates the read oper-
ation by not responding with an acknowledge and then
issuing a stop condition. Refer to figure 8 for the
address, acknowledge, and data transfer sequence.
The device will perform a similar operation called “Set
Current Address” if a stop is issued instead of the
second start shown in figure 9. The device will go into
standby mode after the stop and all bus activity will be
ignored until a start is detected. The effect of this oper-
ation is that the new address is loaded into the
address counter, but no data is output by the device.
X24641
Figure 9. Sequential Read Sequence
Figure 8. Random Read Sequence
SIGNALS
FROM THE
MASTER
SDA BUS
SIGNALS
FROM THE
SLAVE
SIGNALS
FROM THE
MASTER
SDA BUS
SIGNALS
FROM THE
SLAVE
R
S
T
A
T
S
1 0 1 0
ADDRESS
S
ADDRESS
SLAVE
SLAVE
1
A
C
K
0
A
C
K
ADDRESS
DATA
(1)
BYTE 1
A
C
K
A
C
K
8
ADDRESS
DATA
The next Current Address Read operation will read
from the newly loaded address.
Sequential Read
Sequential reads can be initiated as either a current
address read or random read. The first byte is trans-
mitted as with the other modes; however, the master
now responds with an acknowledge, indicating it
requires additional data. The device continues to
output data for each acknowledge received. The
master terminates the read operation by not
responding with an acknowledge and then issuing a
stop condition.
The data output is sequential, with the data from address
n followed by the data from address n + 1. The address
counter for read operations increments through all byte
addresses, allowing the entire memory contents to be
read during one operation. At the end of the address
space the counter “rolls over” to address 0000h and the
device continues to output data for each acknowledge
received. Refer to figure 9 for the acknowledge and data
transfer sequence.
(2)
BYTE 0
A
C
K
A
C
K
S
A
R
T
T
S
ADDRESS
DATA
(n–1)
SLAVE
1
A
C
K
A
C
K
DATA
(n)
DATA
7026 FM 11
O
P
S
T
P
7026 FM 12
S
O
P
P
T