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CAT1021ZI-30 Scheda tecnica(PDF) 7 Page - Catalyst Semiconductor |
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CAT1021ZI-30 Scheda tecnica(HTML) 7 Page - Catalyst Semiconductor |
7 / 21 page CAT1021, CAT1022, CAT1023 © 2007 Catalyst Semiconductor, Inc. 7 Doc. No. 3009 Rev. L Characteristics subject to change without notice DEVICE OPERATION Reset Controller Description The CAT1021/22/23 precision RESET controllers ensure correct system operation during brownout and power up/down conditions. They are configured with open drain RESET outputs. During power-up, the RESET outputs remain active until VCC reaches the VTH threshold and will continue driving the outputs for approximately 200ms (tPURST) after reaching VTH. After the tPURST timeout interval, the device will cease to drive the reset outputs. At this point the reset outputs will be pulled up or down by their respective pull up/down resistors. During power-down, the RESET outputs will be active when VCC falls below VTH. The RESET ¯¯¯¯¯¯ output will be valid so long as VCC is >1.0V (VRVALID). The device is designed to ignore the fast negative going VCC transient pulses (glitches). Reset output timing is shown in Figure 1. Manual Reset Operation The RESET ¯¯¯¯¯¯ pin can operate as reset output and manual reset input. The input is edge triggered; that is, the RESET ¯¯¯¯¯¯ input will initiate a reset timeout after detecting a high to low transition. When RESET ¯¯¯¯¯¯ I/O is driven to the active state, the 200 msec timer will begin to time the reset interval. If external reset is shorter than 200ms, Reset outputs will remain active at least 200ms. The CAT1021/22/23 also have a separate manual reset input. Driving the MR ¯¯¯ input low by connecting a pushbutton (normally open) from MR ¯¯¯ pin to GND will generate a reset condition. The input has an internal pull up resistor. Reset remains asserted while MR ¯¯¯ is low and for the Reset Timeout period after MR ¯¯¯ input has gone high. Glitches shorter than 100ns on MR ¯¯¯ input will not ge- nerate a reset pulse. No external debouncing circuits are required. Manual reset operation using MR ¯¯¯ input is shown in Figure 2. Hardware Data Protection The CAT1021/22/23 supervisors have been designed to solve many of the data corruption issues that have long been associated with serial EEPROMs. Data corruption occurs when incorrect data is stored in a memory location which is assumed to hold correct data. Whenever the device is in a Reset condition, the embedded EEPROM is disabled for all operations, including write operations. If the Reset output(s) are active, in progress communications to the EEPROM are aborted and no new communications are allowed. In this condition an internal write cycle to the memory can not be started, but an in progress internal non- volatile memory write cycle can not be aborted. An internal write cycle initiated before the Reset condition can be successfully finished if there is enough time (5ms) before VCC reaches the minimum value of 2V. In addition, the CAT1021 includes a Write Protection Input which when tied to VCC will disable any write operations to the device. Watchdog Timer The Watchdog Timer provides an independent protection for microcontrollers. During a system failure, CAT1021/22/23 devices will provide a reset signal after a time-out interval of 1.6 seconds for a lack of activity. The CAT1023 is designed with the Watchdog timer feature on the WDI pin. The CAT1021 and CAT1022 monitor the SDA line. If WDI or SDA does not toggle within a 1.6 second interval, the reset condition will be generated on the reset outputs. The watchdog timer is cleared by any transition on a monitored line. As long as reset signal is asserted, the watchdog timer will not count and will stay cleared. |
Codice articolo simile - CAT1021ZI-30 |
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Descrizione simile - CAT1021ZI-30 |
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