68HC11 Learning tools

[Ross Forgione]

I tried this once and was faced with the occasional memory corruption
occouring.

After much frustration and diagnosis (out with the logic analyser ) I
discovered that when powering off the device (cant remember the device
number), That CS would stay High and WE would go low just long enough
for the databus to be loaded into the ram chip at what ever location was
floating on the address bus at the time. (Bummer). The Dallas
chip takes care of this nicely as power and WE/CE (Depending on the
type of chip) are passed through the socket to the ram chip.

Ross

> YOu can also do that yourself by putting a litium 4.5v battery in series with
> a diode to the memory chip, thus preventing the battery from being charged,
> and most ram chips can't be accessed when the voltage is about 4v or less
> (not all, but most), which the diode also does (most small signal diodes have
> a voltage drop of about .6 volts.
> 
> Fred
>