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FM3808 Fiches technique(PDF) 10 Page - Ramtron International Corporation |
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FM3808 Fiches technique(HTML) 10 Page - Ramtron International Corporation |
10 / 27 page N O T R EC O M M EN D ED FO R N EW D ES IG N S La st Ti m e B uy : S ept . 200 6 N o Di re ct Re pl ac em en t Al te rn at e So lu tio n: FM 18 08 +F M 40 05 FM3808 Rev. 1.3 (EOL) Feb. 2006 Page 10 of 27 Supervisor Operation The Supervisor function includes a clock/calendar alarm, a watchdog timer, and a power monitor. A programmable interrupt pin (INT) provides maximum flexibility to the system designer. The INT pin is designed to allow either reset or interrupt capability to the host processor. Alarm The alarm function compares user-programmed values to the corresponding time-of-day values. When a match occurs, the alarm event occurs. The alarm drives an internal flag AF (7FF0 bit D6) and may drive the INT pin if desired. There are four alarm match fields. They are Date, Hours, Minutes, and Seconds. Each of these fields also has a Match bit that is used to determine if the field is used in the alarm match logic. Setting the Match bit to ‘0’ indicates that the corresponding field will be used in the match process. Depending on the Match bits, the alarm can occur as specifically as one particular second on one day of the month, or as frequently as once per second continuously. The MSB of each Alarm register is a Match bit. Examples of the Match bit settings are shown in the table below. Selecting none of the match bits (all ‘1’s) indicates that no match is required. The alarm occurs every second. Setting the match select bit for seconds to ‘0’ causes the logic to match the seconds alarm value to the current time of day. Since a match will occur for only one value per minute, the alarm occurs once per minute. Likewise setting the seconds and minutes match select bits causes an exact match of these values. Thus, an alarm will occur once per hour. Setting seconds, minutes, and hours causes a match once per day. Lastly, selecting all match- values causes an exact time and date match. Selecting other bit combinations will not produce meaningful results, however the alarm circuit should follow the functions described. There are two ways a user can detect an alarm event, by reading the AF flag or monitoring the INT pin. The AF flag in the register 7FF0h (bit D6) will indicate that a date/time match has occurred. The AF bit will be set to 1 when a match occurs. Reading the Flags/Control register clears the alarm flag bit (and all others). A hardware interrupt pin may be used to detect an alarm event. The AIE bit in the register 7FF6h The interrupt function is described below. Alarm Match Bit Examples Seconds Minutes Hours Date Alarm condition 1 1 1 1 No match required = alarm 1/second 0 1 1 1 Alarm when seconds match, = alarm 1/minute 0 0 1 1 Alarm when seconds, minutes match, = alarm 1/hour 0 0 0 1 Alarm when seconds, minutes, hours match, = alarm 1/day 0 0 0 0 Alarm when seconds, minutes, hours, date match, = alarm 1/month |
Numéro de pièce similaire - FM3808_06 |
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Description similaire - FM3808_06 |
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