I'm talking about the chips not the presets
EDIT: Not working on my side
P.S.: Sorry it didn't work for you. Was the chip fully erased (full of 0xFFs)?
P.P.S: Not sure it has an impact but I'm using Win7 Pro SP1 32bit.
sounds like maybe a hardware fault.
cmos chips use 12.5v
nmos chips use 21v or even 25v
upto 27512 is 28pin, over that is 32pin and has the power on different pins.
so maybe there are pin driver problems.
it could be worth checking VDD(pin28/32) and VPP with a meter while trying to program a chip.
and DO NOT power it from the usb cable - specially if it's from a laptop.
had success writing the 27128 chip thanks @Apocalypse with 27128 21v preset and 1ms.
however I have only 27256 12v preset for which doesn't work for both the 256, is there any trick to force the voltage to 21 ?
EDIT : Eprom eraser just died from stress, I guess those chips are cursed
The post was edited 1 time, last by archimage ().
get the datasheets for the eproms and you will know the VPP voltage required.
and i'm pretty sure no nmos (non c variant) used 12.5v
so your programmer has a shit parts database!