Datasheet

Technical Note
13/21
BR24T□□□-W Series
www.rohm.com
2011.1 - Rev.H
© 2011 ROHM Co., Ltd. All rights reserved.
●WP valid timing (write cancel)
WP is usually fixed to 'H' or 'L', but when WP is used to cancel write cycle and so forth, pay attention to the following WP valid timing. During
write cycle execution, in cancel valid area, by setting WP='H', write cycle can be cancelled. In both byte write cycle and page write cycle, the
area from the first start condition of command to the rise of clock to taken in D0 of data(in page write cycle, the first byte data) is cancel
invalid area.
WP input in this area becomes Don't care. Set the setup time to rise of D0 taken SCL 100ns or more. The area from the rise of SCL to take in
D0 to input the stop condition is cancel valid area. And, after execution of forced end by WP, standby status gets in.
●
Command cancel by start condition and stop condition
During command input, by continuously inputting start condition and stop condition, command can be cancelled. (Fig.48)
However, in ACK output area and during data read, SDA bus may output 'L', and in this case, start condition and stop condition cannot be
input, so reset is not available. Therefore, execute software reset. And when command is cancelled by start, stop condition, during random
read cycle, sequential read cycle, or current read cycle, internal setting address is not determined, therefore, it is not possible to carry out
current read cycle in succession. When to carry out read cycle in succession, carry out random read cycle.
・Rise of D0 taken clock
SCL
D0 ACK
Enlarged view
SCL
SDA ACK D0
・Rise of SDA
SDA
WP
WP cancel invalid area
WP cancel valid area
Data is not written.
Fig.47 WP valid timing
Slave
address
D7 D6
D5
D4
D3
D2 D1 D0
Data
tWR
SDA D1
S
T
A
R
T
A
C
K
L
A
C
K
L
A
C
K
L
A
C
K
L
S
T
O
P
Word
address
Fig.48 Case of cancel by start, stop condition during slave address input
SCL
SDA
1 1 0 0
Start condition Stop condition
Enlarged view
WP cancel invalid area