BR24A16-WM(2009) 데이터 시트보기 (PDF) - ROHM Semiconductor
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BR24A16-WM Datasheet PDF : 18 Pages
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BR24A□□-WM series
Technical Note
●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 the end of internal automatic write (tWR) is cancel valid area. And, when it is set WP='H' during tWR,
write is ended forcibly, data of address under access is not guaranteed, therefore, write it once again. (Refer to Fig.49.) After
execution of forced end by WP, standby status gets in, so there is no need to wait for tWR (5ms at maximum).
・Rise of D0 taken clock
SCL
SCL
・Rise of SDA
SDA
D1 D0
Enlarged view
ACK
SDA
D0
ACK
Enlarged view
SDA
S
T Slave
A address
R
T
A
C
K
L
Word
address
A
C
K
L
A
D7 D6 D5 D4
D3 D2
D1 D0
C
K
L
Data
AS
CT
KO
LP
tWR
WP cancel invalid area
WP
WP cancel valid area
Write forced end
Data is not written.
Data not guaranteed
Fig.49 WP valid timing
●Command cancel by start condition and stop condition
During command input, by continuously inputting start condition and stop condition, command can be cancelled.
(Refer to Fig. 50.)
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.
SCL
SDA
1
0
1
0
Start condition Stop condition
Fig.50 Case of cancel by start, stop condition during slave address input
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© 2009 ROHM Co., Ltd. All rights reserved.
12/17
2009.08 - Rev.C
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