UPD4990: Difference between revisions

Revision as of 20:00, 4 March 2012

The uPD4990 is a RTC (Real Time Clock) chip made by NEC, used on MVS boards to keep the calendar's time and date.

It shares the battery-backed RAM's battery and has a separate 32.768kHz crystal clock to run even when power is off.

Official uPD4990A datasheet: [[1]]

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 [[File:mvs_upd4990.jpg|right|thumb|uPD4990 RTC in a (dirty) 1FZS MVS slot.]]
-The uPD4990 is a Real Time Clock (RTC) chip made by NEC, to keep the [[calendar]]'s time and date informations on MVS boards.
+The uPD4990 is a RTC (Real Time Clock) chip made by NEC, used on [[MVS]] boards to keep the [[calendar]]'s time and date.
-It shared the [[battery-backed RAM]]'s battery and had a separate 32.768kHz crystal clock to run when power was off.
+It shares the [[battery-backed RAM]]'s battery and has a separate 32.768kHz crystal clock to run even when power is off.
 ==Datasheet==