I have just taken a program that I got working well on a SiLabs C8051F226 eval board and moved it into an Atmel AT89C4051-24PU. I re-assembled the code the .A51 source file making sure to remove all SiLabs specific code and then produced a HEX file that I programmed into the '4051 part using a standalone programmer. I noted that the program did not appear to be running on the Atmel part so I checked some things as follows:

1) I checked the Hex file to see if it contained reasonable content per the way the program is supposed to work. All looks good there.

2) I checked the prototype board that has the socketed AT89C4051 and see that the VCC and GND look good.

3) The external crystal oscillator is running well at its frequency of 22.118 MHz.

4) The reset signal looks good. Swings directly to +5V upon press of the reset button and falls back to GND in about 0.8 msec upon release of the button (for those that would raise an issue about my use of an R/C reset please desist...this is for a simple home project and I'm ok with pressing the button for now to get the MCU running).

5) I reduced the program to a simple thing that has a jump at the reset vector to address 40h. The program then simply enters a loop to toggle P1.7 high, then back low and a JMP back to address 40h. This program also does not appear to run as I see no activity on P1.7 (it stays high all the time) or on any other pin for that matter - except for VCC on Pin 20, GND on pin 10, RST low on Pin 1, and XTAL signals on Pins 4 & 5.

This is the first time I've ever tried to use these low pin count DIP package MCUs. I am wondering if there is some type of internal setup that has to be done to get these to startup and run even the simplest of programs. I combed through the AT89C4051 data sheet and did not see anything pop out at me.

Anyone else here used one of these recently?

Michael Karas