🚀 go-pugleaf

Hi Thorsten,

I guess your problem is pin 30 (A17 @ 27C020, NOT Connected @ 27C010).
Due to an higher address range of the 27C020 there is one more address line which has to be served. In the case of the less memory chip this line is free and obviously connected to the next pin (# 31 which has to be high during normal read operation) in order not to let the pin floating which can have damaging effects to the device (especially to CMOS types). Check this out in your application with power down and chip off the socket! If so, cut the line on the board if possible and connect pin 30 to GND(pi

n 16). This will select the lower address area in the two Megabit chip and will work with the other as well.

Good luck,

Christian Kral
(Inst. f. Automation, TU Vienna, AUSTRIA)