BU9847GUL-W_10 Datasheet, PDF (11/19 Pages) Rohm – WL-CSP EEPROM family I2C BUS

BU9847GUL-W
Technical Note
●Software reset
Software reset is executed when to avoid malfunction after power on, and to reset during command input. Software reset
has several kinds, and 3 kinds of them are shown in the figure below. (Refer to Fig.43(a), Fig.43(b) and Fig.43(c).) In
dummy clock input area, release the SDA bus (“H” by pull up). In dummy clock area, ACK output and read data “0” (both “L”
level) may be output from EEPROM, therefore, if “H” is input forcibly, output may conflict and over current may flow, leading
to instantaneous power failure of system power source or influence upon devices.
SCL
Dummy clock x14
12
13 14
Start x2
Normal command
SDA
Normal command
Fig.43-(a) The case of dummy clock + START + START + command input
SCL
SDA
Start
1
Dummy clock x9
2
8
Start
9
Normal command
Normal command
Fig.43-(b) The case of START + 9 dummy clocks + START + command input
SCL
SDA
Start x 9
1 23
7 89
Normal command
Normal command
Fig.43-(c) START x 9 + command input
* Start normal command from START input.
●Acknowledge polling
During internal write execution, all input commands are ignored, therefore ACK is not sent back. During internal automatic
write execution after write cycle input, next command (slave address) is sent, and if the first ACK signal sends back “L”,
then it means end of write action, while if it sends back “H”, it means now in writing. By use of acknowledge polling, next
command can be executed without waiting for tWR=5ms.
When to write continuously, R / W = 0, when to carry out current read cycle after write, slave address R / W = 1 is sent,
and if ACK signal sends back “L”, then execute word address input and data output and so forth.
First write command
During internal write,
ACK = HIGH is sent back.
S
T
A
R
T
Write command
S
T
O
P
S
T
A
R
T
Slave A
C
address _K
H
S
T
A
R
T
Slave
address
A
C
K
H
…
tWR
Second write command
…
S
T
A
R
T
Slave ^A
C
address K
H
tWR
S
T Slave
A
R
address
T
A
C
K
L
Word
address
A
C
K
L
Data
AS
CT
KO
LP
After completion of internal write,
ACK = LOW is sent back, so input
next word address and data in
succession.
Fig.44 Case to continuously write by acknowledge polling
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11/18
2010.09 - Rev.A