BU9891GUL-W Rohm, BU9891GUL-W Datasheet - Page 8

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

●Description of operations
●Command mode
© 2010 ROHM Co., Ltd. All rights reserved.
BU9891GUL-W
www.rohm.com
Communications of the Microwire Bus are carried out by SK (serial clock), DI (serial data input),DO (serial data output) ,and
CS (chip select) for device selection.
When to connect one EEPROM to a microcontroller, connect it as shown in Fig.32(a) or Fig.32(b). When to use the input and
output common I/O port of the microcontroller, connect DI and DO via a resistor as shown in Fig.32(b), and connection by 3
lines is available.
In the case of plural connections, refer to Fig. 32 (c).
Communications of the Microwire Bus are started by the first “1” input after the rise of CS. This input is called a start bit. After
input of the start bit, inputs ope code, address and data. Address and data are input all in MSB first manners.
“0” input after the rise of CS to the start bit input is all ignored. Therefore, when there is limitation in the bit width of PIO of the
microcontroller, input “0” before the start bit input, to control the bit width.
Fig.32-(a) Connection by 4 lines
Read (READ)
Write enable (WEN)
Write (WRITE)
Write disable (WDS)
・
・
*Start bit
*1
*2
controller
Micro-
Input the address and the data in MSB first manners.
As for *, input either VIH or VIL.
Acceptance of all the commands of this IC starts at recognition of the start bit.
The start bit means the first “1” input after the rise of CS.
As for read, by continuous SK clock input after setting the read command, data output of the set address starts, and
address data in significant order are sequentially output continuously. (Auto increment function)
When the read and the write all commands are executed, data written in the selected memory cell is automatically deleted, and input data is written.
DO
CS
SK
DI
Command
BU9891GUL-W
CS
SK
DI
DO
*1
*2
Start bit
Fig.32 Connection method with microcontroller
Fig.32-(b) Connection by 3 lines
controller
1
1
1
1
Micro-
DO
CS
SK
Ope code
10
00
01
00
BU9891GUL-W
CS
SK
DI
DO
8/17
A7,A6,A5,A4,A3,A2,A1,A0
A7,A6,A5,A4,A3,A2,A1,A0
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0 0 * * * * * *
1 1 * * * * * *
Address
controller
Fig.32-(c) Connection example of plural devices
Micro-
CS2
CS1
CS0
DO
SK
DI
Device 1
D15~D0(WRITE DATA)
D15~D0(READ DATA)
Device 2
Data
Technical Note
2010.07 - Rev.A
Device 3
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