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X40626V14I-4.5A Datasheet(PDF) 6 Page - Intersil Corporation |
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X40626V14I-4.5A Datasheet(HTML) 6 Page - Intersil Corporation |
6 / 22 page 6 FN8119.0 March 28, 2005 Control Register The Control Register provides the user a mechanism for changing the Block Lock and Watchdog Timer set- tings. The Block Lock and Watchdog Timer bits are nonvolatile and do not change when power is removed. The Control Register is accessed at address FFFFh. It can only be modified by performing a byte write opera- tion directly to the address of the register and only one data byte is allowed for each register write operation. Prior to writing to the Control Register, the WEL and RWEL bits must be set using a two step process, with the whole sequence requiring 3 steps. See "Writing to the Control Register" below. The user must issue a stop after sending this byte to the register to initiate the nonvolatile cycle that stores WD1, WD0, BP2, BP1, and BP0. The X40626 will not acknowledge any data bytes written after the first byte is entered. The state of the Control Register can be read at any time by performing a random read at address FFFFh. Only one byte is read by each register read operation. The X40626 resets itself after the first byte is read. The master should supply a stop condition to be con- sistent with the bus protocol, but a stop is not required to end this operation. RWEL: Register Write Enable Latch (Volatile) The RWEL bit must be set to “1” prior to a write to the Control Register. WEL: Write Enable Latch (Volatile) The WEL bit controls the access to the memory and to the Register during a write operation. This bit is a vola- tile latch that powers up in the LOW (disabled) state. While the WEL bit is LOW, writes to any address, including any control registers will be ignored (no acknowledge will be issued after the Data Byte). The WEL bit is set by writing a “1” to the WEL bit and zeroes to the other bits of the control register. Once set, WEL remains set until either it is reset to 0 (by writing a “0” to the WEL bit and zeroes to the other bits of the control register) or until the part powers up again. Writes to the WEL bit do not cause a nonvolatile write cycle, so the device is ready for the next opera- tion immediately after the stop condition. BP2, BP1, BP0: Block Protect Bits - (Nonvolatile) The Block Protect Bits, BP2, BP1 and BP0, determine which blocks of the array are write protected. A write to a protected block of memory is ignored. The block pro- tect bits will prevent write operations to one of eight segments of the array. WD1, WD0: Watchdog Timer Bits The bits WD1 and WD0 control the period of the Watchdog Timer. The options are shown below. Write Protect Enable These devices have an advanced Block Lock scheme that protects one of eight blocks of the array when enabled. It provides hardware write protection through the use of a WP pin and a nonvolatile Write Protect Enable (WPEN) bit. Four of the 8 protected blocks match the original Block Lock segments and this pro- tection scheme is fully compatible with the current devices using 2 bits of block lock control (assuming the BP2 bit is set to 0). The Write Protect (WP) pin and the Write Protect Enable (WPEN) bit in the Control Register control the programmable Hardware Write Protect feature. Hard- ware Write Protection is enabled when the WP pin and the WPEN bit are HIGH and disabled when either the WP pin or the WPEN bit is LOW. When the chip is Hardware Write Protected, nonvolatile writes as well as to the block protected sections in the memory array cannot be written. Only the sections of the memory array that are not block protected can be written. Note that since the WPEN bit is write protected, it cannot be changed back to a LOW state; so write protection is enabled as long as the WP pin is held HIGH. 76 5 4 3 2 1 0 WPEN WD1 WD0 BP1 BP0 RWEL WEL BP2 Protected Addresses (Size) Array Lock 0 0 0 None (factory setting) None 0 0 1 1800h - 1FFFH (2K bytes) Upper 1/4 (Q4) 0 1 0 1000h - 1FFFH (4K bytes) Upper 1/2 (Q3,Q4) 0 1 1 0000h - 1FFFH (8K bytes) Full Array (All) 1 0 0 000h - 03FH (64 bytes) First Page (P1) 1 0 1 000h - 07FH (128 bytes) First 2 pgs (P2) 1 1 0 000h - 0FFH (256 bytes) First 4 pgs (P4) 1 1 1 000h - 1FFH (512 bytes) First 8 Pgs (P8) WD1 WD0 Typ. Watchdog Time-out Period 0 0 1.4 Seconds 0 1 600 milliseconds 1 0 200 milliseconds 1 1 Disabled (factory setting) X40626 |
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