Greetings,

In a recent project I have begun work on, I notice that my device fails a READ operation according to my oscilloscope. Ironically, the WR# line does operate accordingly. After some experimenting, I have found nothing in the hardware aspect that can explain this cause.

EA# is high, RD# and WR# have no pullups. RST is provided at 200mS. I have tried this on several devices with the same result.

the software uses a simple one-liner to make the read (which fails to work).

#define XBYTE ((unsigned char volatile xdata*)0)
...
c = XBYTE[ 0x80 ];


in case it was the c compiler I tried the following within assembly:

...
MOVX @DPTR, A ; where a=byte read from external address


Any information or ideas would be appreciated.