AT24C512C 查看數據表（PDF） - Atmel Corporation
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AT24C512C Datasheet PDF : 21 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 types of read operations: Current Address Read, Random Address
Read, and 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 on the SDA line. The microcontroller does not respond with an zero, but
does generate a following Stop condition (see Figure 9-3 on page 11).
Random Read: A Random Read requires an initial byte write sequence to load in the data word address. This is known
as a “dummy write” operation. 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 (see
Figure 9-4 on page 11).
Sequential Read: Sequential Reads are initiated by either a Current Address Read or a Random Address Read. After
the microcontroller receives a data word, it responds with an acknowledge. As long as the EEPROM receives an
acknowledge, it will continue to increment the data word address and serially clock out sequential data words. When the
memory address limit is reached, the data word address will roll-over and the sequential read will continue. The
Sequential Read operation is terminated when the microcontroller does not respond with a zero but does generate a
following Stop condition (see Figure 9-5 on page 11).
Figure 9-1. Byte Write
S
W
T
R
A
I
R Device
T
First
T Address
E
Word Address
Second
Word Address
S
T
O
Data
P
SDA Line
M
RA
A
A
A
S
/C
C
C
C
B
WK
K
K
K
Figure 9-2. Page Write
S
W
T
R
A
I
R Device
T
First
T Address E Word Address (n)
Second
Word Address (n)
Data (n)
S
T
O
Data (n + x) P
SDA Line
M
RA
A
A
A
A
S
/C
C
C
C
C
B
WK
K
K
K
K
Atmel AT24C512C [DATASHEET] 10
8720C–SEEPR–7/12
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