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STK12C68-CF25 参数 Datasheet PDF下载

STK12C68-CF25图片预览
型号: STK12C68-CF25
PDF下载: 下载PDF文件 查看货源
内容描述: 8Kx8自动存储的nvSRAM [8Kx8 AutoStore nvSRAM]
分类和应用: 存储静态存储器
文件页数/大小: 20 页 / 526 K
品牌: SIMTEK [ SIMTEK CORPORATION ]
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STK12C68 (SMD5962-94599)  
capacitor having a capacity of between 68μF and  
220μF ( 20%) rated at 6V should be provided.  
SOFTWARE NONVOLATILE RECALL  
A software RECALL cycle is initiated with a sequence  
of READ operations in a manner similar to the soft-  
ware STORE initiation. To initiate the RECALL cycle,  
the following sequence of E controlled READ opera-  
tions must be performed:  
In system power mode (Figure 3), both VCCX and VCAP  
are connected to the + 5V power supply without the  
68μF capacitor. In this mode the AutoStore function  
of the STK12C68 will operate on the stored system  
charge as power goes down. The user must, how-  
ever, guarantee that VCCX does not drop below 3.6V  
during the 10ms STORE cycle.  
1. Read address  
2. Read address  
3. Read address  
4. Read address  
5. Read address  
6. Read address  
0000 (hex)  
1555 (hex)  
0AAA (hex)  
1FFF (hex)  
10F0 (hex)  
0F0E (hex)  
Valid READ  
Valid READ  
Valid READ  
Valid READ  
Valid READ  
Initiate RECALL cycle  
If an automatic STORE on power loss is not required,  
then VCCX can be tied to ground and + 5V applied to  
VCAP (Figure 4). This is the AutoStore Inhibit mode, in  
which the AutoStore function is disabled. If the  
STK12C68 is operated in this configuration, refer-  
ences to VCCX should be changed to VCAP throughout  
this data sheet. In this mode, STORE operations may  
be triggered through software control or the HSB pin.  
It is not permissible to change between these three  
options “on the fly.”  
Internally, RECALL is a two-step procedure. First, the  
SRAM data is cleared, and second, the nonvolatile  
information is transferred into the SRAM cells. After  
the tRECALL cycle time the SRAM will once again be  
ready for READ and WRITE operations. The RECALL  
operation in no way alters the data in the Nonvolatile  
Elements. The nonvolatile data can be recalled an  
unlimited number of times.  
In order to prevent unneeded STORE operations,  
automatic STOREs as well as those initiated by  
externally driving HSB low will be ignored unless at  
least one WRITE operation has taken place since the  
most recent STORE or RECALL cycle. Software initi-  
ated STORE cycles are performed regardless of  
whether a WRITE operation has taken place. An  
optional pull-up resistor is shown connected to HSB.  
This can be used to signal the system that the  
AutoStore cycle is in progress.  
AutoStore OPERATION  
The STK12C68 can be powered in one of three  
modes.  
During normal AutoStore operation, the STK12C68  
will draw current from VCCX to charge a capacitor  
connected to the VCAP pin. This stored charge will be  
used by the chip to perform a single STORE opera-  
tion. After power up, when the voltage on the VCAP  
pin drops below VSWITCH, the part will automatically  
disconnect the VCAP pin from VCCX and initiate a  
STORE operation.  
If the power supply drops faster than 20 μs/volt  
before VCCX reaches VSWITCH, then a 2.2 ohm resistor  
should be inserted between VCCX and the system  
supply to avoid momentary excess of current  
between Vccx and Vcap.  
Figure 2 shows the proper connection of capacitors  
for automatic store operation. A charge storage  
28  
27  
26  
1
1
28  
27  
26  
1
28  
27  
26  
+
14  
15  
14  
15  
14  
15  
Figure 4. AutoStore Inhibit Mode  
Figure 3. System Power Mode  
Figure 2. AutoStore Mode  
Rev 0.7  
Document Control #ML0008  
February 2007  
10