2-WIRE CMOS SERIAL E2PROM
S-24CS01A/02A/04A/08A
Rev.4.4_00
7. 2 Random Read
Random read is used to read the data at an arbitrary memory address.
A dummy write is performed to load the memory address into the address counter.
When the E2PROM receives a 7-bit device address and a 1-bit read / write instruction code set to "0"
following a start condition, it responds with an acknowledge. The E2PROM then receives an 8-bit word
address and responds with an acknowledge. The memory address is loaded to the address counter in the
E2PROM by these operations. Reception of write data does not follow in a dummy write whereas reception
of write data follows in a byte write and in a page write.
Since the memory address is loaded into the memory address counter by dummy write, the master device
can read the data starting from the arbitrary memory address by transmitting a new start condition and
performing the same operation in the current address read.
That is, when the E2PROM receives a 7-bit device address and a 1-bit read / write instruction code set to
"1", following a start condition signal, it responds with an acknowledge. Next, 8-bit data is transmitted from
the E2PROM in synchronous to the SCL clock. The master device outputs stop condition not an
acknowledge , the reading of E2PROM is ended.
S
T
A
R
T
S
T
A
R
T
W
R
I
R
E
A
D
S
T
NO ACK from
Master Device
O
P
DEVICE
WORD
DEVICE
T
E
DATA
ADDRESS
ADDRESS (n)
ADDRESS
SDA
LINE
1
0
1
0 A2 A1 A0 0
W7W6W5W4W3W2W1W0
1
0
1
0 A2 A1 A0 1
D7 D6 D5 D4 D3 D2 D1 D0
M
S
B
L R A
R
/
L
A
C
K
A
C
K
M
S
B
S
/
C
S
B
B W K
W
ADR INC
DUMMY WRITE
Remark1. A1 is P1 in the S-24CS08A.
2. A0 is P0 in the S-24CS04A/08A.
3. W7 is optional in the S-24CS01A.
Figure 17 Random Read
17
Seiko Instruments Inc.
SII [ SEIKO INSTRUMENTS INC ]
