AT34C02 データシートの表示（PDF） - Atmel Corporation
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コンポーネント説明
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AT34C02 Datasheet PDF : 12 Pages
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WP Connected to GND or Floating
Acknowledgment
Start R/W Bit Write Protect Register
from Device
1010
R
X
ACK
1010
W
Programmed
ACK
1010
W
Not Programmed
ACK
0110
R
Programmed
No ACK
0110
R
Not Programmed
ACK
0110
W
Programmed
No ACK
0110
W
Not Programmed
ACK
WP Connected to VCC
1010
R
X
ACK
1010
W
Programmed
ACK
1010
W
Not Programmed
ACK
0110
R
Programmed
No ACK
0110
R
Not Programmed
ACK
0110
W
Programmed
No ACK
0110
W
Not Programmed
ACK
Figure 1. Setting Write Protect Register
SDA LINE
S
T
CONTROL
A
BYTE
R
T
0110
0
A
C
K
Action from Device
Read Array
Can Write to First Half Only
Can Write to Full Array
Stop - Indicates Write Protect Register is Programmed
Read Out Data Don’t Care. Indicates WP Register is Not Prog
Stop - Indicates Write Protect Register is Programmed
Program Write Protect Register (irreversible)
Read Array
Device Write Protect
Device Write Protect
Stop - Indicates Write Protect Register is Programmed
Read Out Data Don’t Care. Indicates WP Register is Not Prog
Stop - Indicates Write Protect Register is Programmed
Cannot Program Write Protect Register
WORD
ADDRESS
S
DATA
T
O
P
A
A
C
C
K
K
Read Operations
Read operations are initiated the same way as write opera-
tions 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
and sequential read.
CURRENT ADDRESS READ: The internal data word
address counter maintains the last address accessed dur-
ing 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. To end
the command, the microcontroller does not respond with an
input zero but does generate a following stop condition
(refer to Figure 5).
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. To end the command, the microcontroller
does not respond with a zero but does generate a following
stop condition (refer to Figure 6).
8
AT34C02
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