UPD4990: Difference between revisions

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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 Real Time Clock (RTC) chip made by NEC, to keep the [[calendar]]'s time and date informations on MVS boards.


It shared the [[SRAM]]'s battery and had a separate 32.768kHz crystal clock to run when power was off.
It shared the [[battery-backed RAM]]'s battery and had a separate 32.768kHz crystal clock to run when power was off.
 
==Datasheet==
 
Official uPD4990A datasheet: [[http://www.datasheetcatalog.org/datasheet/nec/UPD4990AC.pdf]]


[[Category:Chips]]
[[Category:Chips]]

Revision as of 22:00, 6 March 2011

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.

It shared the battery-backed RAM's battery and had a separate 32.768kHz crystal clock to run when power was off.

Datasheet

Official uPD4990A datasheet: [[1]]