S-34C02A Datasheet, PDF (17/34 Pages) Seiko Instruments Inc – 2-WIRE CMOS SERIAL E2PROM FOR DIMM SERIAL PRESENCE DETECT

2-WIRE CMOS SERIAL E2PROM FOR DIMM SERIAL PRESENCE DETECT
Rev.1.2_00
S-34C02A
7. Read
7. 1 Current Address Read
Both in the Write and Read operation, the S-34C02A maintains the memory address that is one the S-34C02A
received when it has accessed last time. The memory address is maintained unless the power supply voltage is
equal to the current address hold voltage V_AH or less. Therefore as long as the master device acknowledges the
position where the address pointer is, data can be read by the memory address of an address pointer without
specifying the word address. This is the current address Read.
The following is about the case that an address counter in the S-34C02A is in “n”.
When the S-34C02A receives the 7-bit device address and the Read/Write instruction code “1” after receiving a
start condition, it generates an acknowledgment signal.
Next, 8-bit data at address n is input from the S-34C02A synchronizing with a SCL clock. At the same time an
address counter is incremented at a falling edge of SCL clock right after the output of 8th bit data, so that address
n+1 is contained in an address counter. The Read operation ends when the master device outputs a stop condition,
not an acknowledgment signal.
S
T
R
E
NO ACK from
Master Device
S
T
A
A
O
R
D
P
T
DEVICE
ADDRESS
DATA
SDA LINE
1 0 1 0 A2 A1 A0 1
D7 D6 D5 D4 D3 D2 D1 D0
M
LR A
S
S/ C
B
BW K
ADR INC
Figure 13 Current Address Read
Regarding the recognition of address pointer, pay the attention to the following;
In the Read operation, a memory address counter in the S-34C02A is automatically incremented every time at a
falling edge of the SCL clock right after the output of 8th bit data. However, in the Write operation, a memory
address counter is not be incremented because the higher 4 bits of the memory address (the higher 4 bits of the
word address) are fixed every time at a falling edge of the SCL clock right after the receipt of 8th bit data.
Seiko Instruments Inc.
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