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X5045M8I-2.7 Datasheet(PDF) 3 Page - Xicor Inc. |
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X5045M8I-2.7 Datasheet(HTML) 3 Page - Xicor Inc. |
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3 / 20 page  X5043/X5045 Characteristics subject to change without notice. 3 of 20 REV 1.1.2 5/29/01 www.xicor.com PRINCIPLES OF OPERATION Power On Reset Application of power to the X5043/X5045 activates a Power On Reset Circuit. This circuit pulls the RESET/ RESET pin active. RESET/RESET prevents the sys- tem microprocessor from starting to operate with insuf- ficient voltage or prior to stabilization of the oscillator. When VCC exceeds the device VTRIP value for 200ms (nominal) the circuit releases RESET/RESET, allowing the processor to begin executing code. Low Voltage Monitoring During operation, the X5043/X5045 monitors the VCC level and asserts RESET/RESET if supply voltage falls below a preset minimum VTRIP. The RESET/RESET signal prevents the microprocessor from operating in a power fail or brownout condition. The RESET/RESET signal remains active until the voltage drops below 1V. It also remains active until VCC returns and exceeds VTRIP for 200ms. Watchdog Timer The Watchdog Timer circuit monitors the microproces- sor activity by monitoring the WDI input. The micropro- cessor must toggle the CS/WDI pin periodically to prevent an active RESET/RESET signal. The CS/WDI pin must be toggled from HIGH to LOW prior to the expiration of the watchdog time out period. The state of two nonvolatile control bits in the Status Register determines the watchdog timer period. The micropro- cessor can change these watchdog bits. With no microprocessor action, the watchdog timer control bits remain unchanged, even during total power failure. VCC Threshold Reset Procedure The X5043/X5045 is shipped with a standard VCC threshold (VTRIP) voltage. This value will not change over normal operating and storage conditions. How- ever, in applications where the standard VTRIP is not exactly right, or if higher precision is needed in the VTRIP value, the X5043/X5045 threshold may be adjusted. The procedure is described below, and uses the application of a high voltage control signal. Setting the VTRIP Voltage This procedure is used to set the VTRIP to a higher volt- age value. For example, if the current VTRIP is 4.4V and the new VTRIP is 4.6V, this procedure will directly make the change. If the new setting is to be lower than the current setting, then it is necessary to reset the trip point before setting the new value. To set the new VTRIP voltage, apply the desired VTRIP threshold voltage to the VCC pin and tie the WP pin to the programming voltage VP. Then send a WREN com- mand, followed by a write of Data 00h to address 01h. CS going HIGH on the write operation initiates the VTRIP programming sequence. Bring WP LOW to com- plete the operation. Note: This operation also writes 00h to array address 01h. Figure 1. Set VTRIP Level Sequence (VCC = desired VTRIP value.) 012 345 67 SCK SI CS 06h 012 345 67 89 10 12 13 14 15 8 Bits 01h 02h WP VPE = 15-18V 00h WREN Write Address Data 11 |
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