24C128C 데이터 시트보기 (PDF) - Atmel Corporation
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24C128C Datasheet PDF : 23 Pages
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9. Read Operations
Read operations are initiated the same way as write operations with the exception that the read/write select bit
in the device address word is set to one. There are three read operations:
Current Address Read
Random Address Read
Sequential Read
Current Address Read: The internal data word address counter maintains the last address accessed during
the last read or write operation, incremented by one. This address stays valid between operations as long as the
chip power is maintained. The address roll-over during read is from the last byte of the last memory page, to the
first byte of the first page.
Once the device address with the read/write select bit set to one is clocked in and acknowledged by the
EEPROM, the current address data word is serially clocked out. The microcontroller does not respond with an
input zero but does generate a following stop condition.
Figure 9-1. Current Address Read
S
T
A
R
Device
T Address
SDA Line
M
S
B
R
E
A
D
RA
/C
WK
Data
S
T
O
P
N
O
A
C
K
Random Read: A Random Read requires a dummy byte write sequence to load in the data word address. Once
the device address word and data word address are clocked in and acknowledged by the EEPROM, the
microcontroller must generate another start condition. The microcontroller now initiates a Current Address Read
by sending a device address with the read/write select bit high. The EEPROM acknowledges the device
address and serially clocks out the data word. The microcontroller does not respond with a zero but does
generate a following stop condition.
Figure 9-2. Random Read
S
W
T
R
A
I
R
Device
T
T Address
E
First Word
Address
Second Word
Address
S
T
R
A
E
R
Device
A
T
Address
D
SDA LINE
M
RA
A
LA
S
/C
C
SC
B
WK
K
BK
RA
/C
WK
Note: * = Don’t care bit
Dummy Write
Data (n)
S
T
O
P
N
O
A
C
K
AT24C128C [DATASHEET] 11
Atmel-8734D-SEEPROM-AT24C128C-Datasheet_082015
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