Oops; received this after sending mine. Writes will definitely fail; I'm just curious whether outputs are enabled with /OE low and /PGM also low.
On Mon, Nov 14, 2022 at 10:24 AM Brian K. White <[email protected]> wrote: > On 11/14/22 10:11, Brian K. White wrote: > > On 11/14/22 09:12, Brian White wrote: > >> The datasheet says to rest vpp at vcc. Most do, even if elsewhere they > >> also say that writing is disabled as long as vpp is below vpp and the > >> only low limit is pretty much the same as for any other pin, like 0.5 > >> or 0.7 below vcc. > > > > derp I mean the low limit is a little below GND or VSS not VCC. > > Although a Microchip 27C64 datasheet I happen to be looking at at the > > moment does actually say the vpp read voltage is min vcc-0.7, max vcc. > > More derp, I obviously confused VPP with /WE there. > But pin 27, being /WE (/PGM), still needs to be held at VCC not GND, > although theoretically any writes should still fail without VPP, but > still, you just hold /WE at VCC for reads. > > -- > bkw > >
