Re: [Sdcc-user] [OT] AT89S8252

[Kai H. <M5...@ha...>]

Hi there,

"van de Werken, Matthew (DEM, PH)" wrote:
> * Running 24MHz XTAL --> looks good on the 'scope.
> * Port 0 --> strange oscillations on this port (with 10k pull-ups), at
> around 2MHz, with a single spike followed by a longer (double-length) spike
> (500ns, then 500ns low, then 1usec high, then 500nsec low, then 500nsec
> high, etc).

> * Port 2 --> 2.0 has a 3.9kHz sq. wave; 2.1 has 1.95kHz sq. wave, and so on,
> halving in frequency up to p2.7.
> * Ports 1&3 seem to have random values assigned.

Did you check the /EA Pin. If it is strapped to GND the uC tries to
fetch its program from external memory. In this mode Port 2 is the
Adressbus (A8 .. A15) and Port 0 is a multiplexed Adress- and Databus
(A0 .. A7 and D0 .. D7), which explains the single spike (probably the
data strobe) and the halving frequencies. 

To use the internal flashrom the /EA pin has to be pulled-up to Vcc.

I hope this'll help you and good luck

Kai Hingst