Communication Problems With P89C668

[bong.cruz]

The 89C668 sometimes can communicate to the flash magic; but not all the time; I got 89c668 this morning and communicate properly to the flash magic, then after powering it down for an hour or so; this 89c668 does not communicate anymore; the error I got " adjust the baud rate by lowering up or down; One of them I did replaced the 89c668 thinking it was bad IC however it took a while before the flash magic communicate to this IC; but after that I can load our program BIOS I can do anything on it then turn it off; The next morning I can communicate again? Please give more info about this 89c668?
Even thou it does not communicate to the flash magic; I can make it communicate with the hyperterminal ?? why? Bong.cruz  Sr. Engr.Tech

[Andy Ayre]

In future please start a new topic for a new problem. I've moved your post to a new topic.

Please generate a debug file as described in the following posting and send it to me for evaluation.

  http://forum.flashmagictool.com/index.php?topic=3272.0

Andy

[bong.cruz]

Hello Andy,

I did follow your advice by pulling the P2.6 (30) P2.7 (31) at H. By doing this it did communicate to the flash magic; however, our schematic show that P2.7 was not connected at all and P2.6 was already pull high. The other model was the other way around. However, even thou the P2.6 was not connected still measure a 5 volts, I don't know where is coming from so I did I connected a resistor and connect at 5volts, then start communicating. I will try the rest of the board.
What happened if this P2.6 or P2.7 are not pulled H? what page of the data sheet that they need to be pulled H?

BOng

[Andy Ayre]

Originally this was an undocumented requirement. I'm not sure if that changed in later years. If they are not pulled high then the bootloader appears to become unreliable. For example not always responding or responding with strange things.

If P2.6 was at 5V with no load then it was probably set to high-impedence mode.

Andy