Datasheet

Technical Note
12/21
BR24T□□□-W Series
www.rohm.com
2011.1 - Rev.H
© 2011 ROHM Co., Ltd. All rights reserved.
●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.45-(a), Fig.45-(b), Fig.45-(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.
●
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.
1 2 13
14
SCL
Dummy clock×14
Start×2
SCL
Fig.45-(a) The case of dummy clock +START+START+ command input
タト
※Start command from START input.
2 1 8 9
Dummy clock×9
Start
Fig.45-(b) The case of START +9 dummy clocks +START+ command input
Start
Normal command
Normal command
Normal command
Normal command
Start×9
SDA
SDA
SCL
SD
1 2 3 8 9 7
Fig.45-(c) START×9+ command input
Normal command
Normal command
SDA
Slave
address
Word
address
…
…
S
T
A
R
T
First write command
A
C
K
H
A
C
K
L
Slave
address
Slave
address
Slave
address
Data
Write command
During internal write,
ACK = HIGH is sent back.
After completion of internal write,
ACK=LOW is sent back, so input
next word address and data in
succession.
tWR
tWR
Second write command
S
T
A
R
T
S
T
A
R
T
S
T
A
R
T
S
T
A
R
T
S
T
O
P
S
T
O
P
A
C
K
H
A
C
K
H
A
C
K
L
A
C
K
L
Fig.46 Case to continuously write by acknowledge polling