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X24645P 参数 Datasheet PDF下载

X24645P图片预览
型号: X24645P
PDF下载: 下载PDF文件 查看货源
内容描述: 先进的2线串行é 2 PROM带座锁TM保护 [Advanced 2-Wire Serial E 2 PROM with Block Lock TM Protection]
分类和应用: 内存集成电路光电二极管可编程只读存储器电动程控只读存储器电可擦编程只读存储器时钟
文件页数/大小: 18 页 / 86 K
品牌: XICOR [ XICOR INC. ]
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X24645  
WEL and RWEL are volatile latches that power-up in  
the LOW (disabled) state. A write to any address other  
than 1FFFh, where the Write Protect Register is  
located, will be ignored (no ack) until the WEL bit is set  
HIGH. The WEL bit is set by writing 0000001x to  
address 1FFFh. Once set, WEL remains HIGH until  
either reset (by writing 00000000 to 1FFFh) or until the  
part powers-up again. The RWEL bit controls writes to  
the block protect bits. RWEL is set by first setting WEL  
to “1” and then writing 0000011x to address 1FFFh.  
RWEL must be set in order to change the block protect  
bits, BP0 and BP1, or the WPEN bit. RWEL is reset  
when the block protect or WPEN bits are changed, or  
when the part powers-up again.  
WRITE PROTECT REGISTER  
The Write Protect Register (WPR) is located at the  
highest address, 1FFFh.  
Figure 11. Write Protect Register  
WPR (ADDR = 1FFFh)  
7
6
5
4
3
1
0
2
WPEN  
0
0
BP1  
BP0  
WEL  
0
RWEL  
2783 ILL F15.1  
WPR.1 = WEL  
– “Write Enable” Latch (Volatile)  
0 = Write enable latch reset, writes disabled  
1 = Write enable latch set, writes enabled  
Programming the BP or WPEN Bits  
A three step sequence is required to change the  
nonvolatile Block Protect or Write Protect Enable:  
If WEL = “0” then “no ACK” after first byte of input data.  
WPR.2 = RWEL  
1) Set WEL = 1 (write 00000010 to address 1FFFh,  
volatile write cycle)  
– “Register Write Enable” Latch (Volatile)  
0 = Register write enable latch reset, writes dis-  
abled  
(Start)  
1 = Register write enable latch set, writes enabled  
2) Set RWEL = 1 (write 00000110 to address 1FFFh,  
volatile write cycle)  
WPR.3, WPR.4 = BP0, BP1  
– Block Protect Bits (Nonvolatile)  
(See Block Protect section for definition)  
(Start)  
WPR.7 = WPEN  
– Write Protect Enable Bit (Nonvolatile)  
(See Hardware Write Protect section for definition)  
3) Set BP1, BP0, and/or WPEN bits (Write w00yz010  
to address 1FFFh)  
w = WPEN, y = BP1, Z = BP0,  
(Stop)  
Writing to the Write Protect Register  
The Write Protect Register is written by performing a  
random write of one byte directly to address, 1FFFh. If  
a page write is performed starting with any address  
other than 1FFF, the byte in the array at address  
1FFFh will be written instead of the Write Protect  
Register (assuming writes are not disabled by the  
block protect register).  
Step 3 is a nonvolatile write cycle, requiring 10ms to  
complete. RWEL is reset to “0” by this write cycle,  
requiring another write cycle to set RWEL again before  
the block protect bits can be changed. RWEL must be  
“0” in step 3; if w00yz110 is written to address 1FFFh,  
RWEL is set but WPEN, BP1 and BP0 are not  
changed (the device remains at step 2).  
The state of the Write Protect Register can be read by  
performing a random read at address 1FFFh at any  
time. If a sequential read starting at any other address  
than 1FFFh is performed, the contents of the byte in  
the array at 1FFFh is read out instead of the Write  
Protect Register.  
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