I have been programming on this mpu and everything seem to be working just fine, then all of the sudden, nothing worked any more ???? I keeped removing sections of circiutry from my board until the only thing left was the cristal, an Inverter, two led and the bypass cap. Still nothing woks properly.

I run my very very simple progam in the s51 simulator and it runs, It should, it can get any simpler:

#include <at89s2852.h>

void main( )
{
P1 = 0x55;
while(1==1){};
}

I can load this to the mpu and verify that it is loaded correctly.

Here is the schematic. Ground and the crystal are connected of course. If they weren't you couldn't get the program to load.

+5v                                        +5v
---                                        ---
 |                          ____________    |
 +-----------(1k ohm)---+--|p1.0     VCC|---+
 |                      |  |            |   |
 +---(led)---(inverter)-+  |            | (1µf)
 |                         |            |   |
 +-----------(1k ohm)---+--|p1.1        |  gnd
 |                      |  |            |
 +---(led)---(inverter)-+  |            |

After downloading, verifying and resetting the chip, one of the two led's should be off and the other lit. But in my case both of them are lit( p1.0 and p0.1 are both hi).

Is everything ok with this little test.