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ST25W08B6TR 数据表(PDF) 10 Page - STMicroelectronics |
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ST25W08B6TR 数据表(HTML) 10 Page - STMicroelectronics |
10 / 16 page The sequence is as follows: – Initial condition: a Write is in progress (see Fig- ure 8). – Step 1: the Master issues a START condition followed by a Device Select byte (1st byte of the new instruction). – Step 2: if the memory is busy with the internal write cycle, no ACK will be returned and the master goes back to Step 1. If the memory has terminated the internal write cycle, it will respond with an ACK, indicating that the mem- ory is ready to receive the second part of the next instruction (the first byte of this instruc- tion was already sent during Step 1). Write Protection. Data in the upper block of 256 bytes of the memory may be write protected. The memory is write protected between a boundary address and the top of memory (address 3FFh) when the PRE input pin is taken high and when the Protect Flag (bit b2 in location 3FFh) is set to ’0’. The boundary address is user defined by writing it in the Block Address Pointer. The Block Address Pointer is an 8 bit EEPROM register located at the address 3FFh. It is composed by 4 MSBs Address Pointer, which defines the bottom boundary ad- dress, and 4 LSBs which must be programmed at ’0’. This Address Pointer can therefore address a DEVICE OPERATION (cont’d) boundary in steps of 16 bytes. The sequence to use the Write Protected feature is: – write the data to be protected into the top of the memory, up to, but not including, location 3FFh; – set the protection by writing the correct bottom boundary address in the Address pointer (4 MSBs of location 3FFh) with the bit b2 (Protect flag) set to ’0’. Note that for a correct fonctionality of the memory, all the 4 LSBs of the Block Address Pointer must also be programmed at ’0’. The area will now be protected when the PRE input pin is taken High. While the PRE input pin is read at ’0’ by the mem- ory, the location 3FFh can be used as a normal EEPROM byte. Caution: Special attention must be used when using the protect mode together with the Multibyte Write mode (MODE input pin High). If the Multibyte Write starts at the location right below the first byte of the Write Protected area, then the instruction will write over the first 7 bytes of the Write Protected area. The area protected is therefore smaller than the content defined in the location 3FFh, by 7 bytes. This does not apply to the Page Write mode as the address counter ’roll-over’ and thus cannot go above the 16 bytes lower boundary of the protected area. BYTE WRITE DEV SEL BYTE ADDR DATA IN MULTIBYTE AND PAGE WRITE DEV SEL BYTE ADDR DATA IN 1 DATA IN 2 AI00793 DATA IN N ACK ACK ACK R/W ACK ACK ACK R/W ACK ACK Figure 9. Write Modes Sequence (ST24/25C08) 10/16 ST24/25C08, ST24/25W08 |
类似零件编号 - ST25W08B6TR |
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类似说明 - ST25W08B6TR |
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