BU9891GUL-W Rohm, BU9891GUL-W Datasheet - Page 13

• Manufacturer Part Number: BU9891GUL-W
• Description: WL-CSP EEPROM family Microwire Bus
• Manufacturer: Rohm

© 2010 ROHM Co., Ltd. All rights reserved.
BU9891GUL-W
www.rohm.com
6) When to directly connect DI and DO
This IC has independent input terminal DI and output terminal DO, and separate signals are handled on timing chart,
meanwhile, by inserting a resistance R between these DI and DO terminals, it is possible to carry out control by 1 control
line.
○Data collision of microcontroller DI/O output and DO output and feedback of DO output to DI input.
Note) As for the case (2), attention must be paid to the following.
Drive from the microcontroller DI/O output to DI input on I/O timing, and signal output from DO output occur at the same
time in the following points.
(1) 1 clock cycle to take in A0 address data at read command
(2) Timing of CS = “H” after write command. DO terminal in READY / BUSY function output.
Feedback input at timing of these (1) and (2) does not cause disorder in basic operations, if resistance R is inserted.
Dummy bit “0” is output to DO terminal.
→When address data A0 = “1” input, through current route occurs.
When the next start bit input is recognized, “HIGH-Z” gets in.
→Especially, at command input after write, when CS input is started with microcontroller DI/O output “L”,
READY output “H” is output from DO terminal, and through current route occurs.
When status READY is output, DO and DI are shared, DI=”H” and the microcontroller DI/O=”High-Z” or the microcontroller DI/O=”H”,if SK clock is
input, DO output is input to DI and is recognized as a start bit, and malfunction may occur. As a method to avoid malfunction, at status READY
output, set SK=“L”, or start CS within 4 clocks after “H” of READY signal is output.
EEPROM CS input
EEPROM SK input
EEPROM DI input
EEPROM DO output
Microcontroller DI/O port
Fig.50 Collision timing at read data output at DI, DO direct connection
Fig.52 Start bit input timing at DI, DO direct connection
Fig.51 Collision timing at DI, DO direct connection
CS
SK
DI
DO
Fig.49 DI, DO control line common connection
EEPROM CS input
EEPROM SK input
EEPROM DI input
EEPROM DO output
Microcontroller DI/O port
Microcontroller output
Write command
Write command
Write command
Write command
Write command
READY
Microcontroller
Microcontroller output
“H”
High-Z
Start bit
DI/O PORT
13/17
BUSY
Microcontroller input
BUSY
A1
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～ ～
～ ～
～ ～
～ ～
A1
R
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A0
A0
0
Microcontroller input
READY
READY
High-Z
D15 D14 D13
DI
DO
EEPROM
Collision of DI input and DO output
Because DI=”H”, set
SK=”L” at CS rise.
Microcontroller output
～ ～
～ ～
～ ～
～ ～
～ ～
High-Z
READY
Collision of DI input and DO output
High-Z
Technical Note
2010.07 - Rev.A
Datasheet pdf - http://www.DataSheet4U.net/