the only difference between a WDC65C51N and a WDC65C51S is it's missing parity generator/checker. therefore the WDC65C51N is less product for the exact same price. neither datasheet says anything about not being able to be wire-or'ed

as for the DS1813. the DS1813 econoreset is a reset timer and monitor which also triggers if the vcc rail goes under a certain voltage. (and indeed holds reset low for 150ms if it was pulled low on the wire itself by anything else, such as a push button or some i/o port with a diode or a transistor (systems should always be able to hard reset -themselves-. it's quite annoying not to have that, or to have 3 different methods of doing so such as on the pc, none of which are -guaranteed- to work on all pcs hooking it up to nmi implies that it will also pull nmi while the system powers off or during voltage dips that last long enough to empty out the capacitors a bit (in fact if there is one both on reset and on nmi they will pull both in random order, also during powerup there is a good chance nmi goes high a few milliseconds after reset, probably making users end up in your machine language monitor that probably have no business there

hooking up a DS1813 to nmi at the 'first stage' power supply rectifying followed by a current limiting resistor and diode and then a whole bunch of capacitors to keep power up for about 10 seconds or more. with the actual RESET ds1813 there, does allow the system to fully wipe all ram when the power is compromised as apperantly it's too much to ask of memory suppliers to simply provide a reset line which resets all cells anyway, making sure the data is gone once and for all (those people clearly never heard of 'security' . more of an issue with dram than with sram anyway but some srams are 'fake' sram. just being dram with internal refresh logic. therefore also retaining data for months if put in the fridge at the right time.

psu ---ds1813nmivcc---/\/\/\--->|---ds1313resetvcc---

also this can be used to signal some alarms if the power was tampered with. (although the unit going offline would also indicate that already)

Not sure from where you are getting your info, but the W65C51S is sold as dice, not a complete package. Both versions have open drain IRQ outputs.

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