參數(shù)資料
型號: 24LC52-ST
廠商: Microchip Technology Inc.
元件分類: EEPROM
英文描述: 2K 2.5V I 2 C Serial EEPROM with Software Write Protect
中文描述: 2K 2.5VI 2 C串行EEPROM,帶有軟件寫保護(hù)
文件頁數(shù): 6/12頁
文件大小: 81K
代理商: 24LC52-ST
24LCS52
DS21166B-page 6
Preliminary
1996 Microchip Technology Inc.
5.0
ACKNOWLEDGE POLLING
Since the device will not acknowledge during a write
cycle, this can be used to determine when the cycle is
complete (this feature can be used to maximize bus
throughput). Once the stop condition for a write com-
mand has been issued from the master, the device ini-
tiates the internally timed write cycle. ACK polling can
be initiated immediately. This involves the master send-
ing a start condition followed by the control byte for a
write command (R/W = 0). If the device is still busy with
the write cycle, then no ACK will be returned. If the
cycle is complete, then the device will return the ACK
and the master can then proceed with the next read or
write command. See Figure 5-1 for flow diagram.
FIGURE 5-1:
ACKNOWLEDGE POLLING
FLOW
Send
Write Command
Send Stop
Condition to
Initiate Write Cycle
Send Start
Send Control Byte
with R/W = 0
Did Device
Acknowledge
(ACK = 0)
Next
Operation
NO
YES
6.0
WRITE PROTECTION
The 24LCS52 has a software write protect feature that
allows the lower half of the array (addresses 00h - 7Fh)
to be permanently write protected, as well as a WP pin
that can be used to protect the entire array.
6.1
Software Write Protect
The software write protect feature is invoked by writing
to the write protect register. This is done by sending a
command similar to a normal write command. As
shown in Figure 6-1, the write protect register is written
by sending a write command with the slave address set
to 0110 instead of 1010 and the address bits and data
bits are don’t cares. Once the software write protect
register has been written, the device will not acknowl-
edge the 0110 control byte.
Once the software write
protect register has been written, the write protec-
tion is enabled and cannot be reversed, even if the
device is powered down.
6.2
Hardware Write Protect
The WP pin can be tied to Vcc, V
SS
, or left floating. If
tied to V
CC
, the entire array will be write protected,
regardless of whether the software write protect regis-
ter has been written or not. If the WP pin is set to V
CC
,
it will prevent the software write protect register from
being written. If the WP is tied to V
SS
or left floating,
then write protection is determined by the status of the
software write protect register.
FIGURE 6-1:
SETTING WRITE PROTECT REGISTER
S
P
BUS ACTIVITY
MASTER
SDA LINE
BUS ACTIVITY
S
T
A
R
T
S
T
O
P
CONTROL
BYTE
WORD
ADDRESS
DATA
A
C
K
A
C
K
A
C
K
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