Greetings to the group. I'm new to this list,but have been using 8051/52 microcontrollers for quite a number of years. Also been lurking for a while now ;-)

I recently received some Atmel AT89S8253's in the TQFP pack and have been having some problems getting them to start up. They either start up on the wrong frequency (much slower - around 7MHz for a 24MHz crystal) or not at all. I'm guessing that this is due to the 5pF oscillator load vs. the typical 30pF load with other devices. I've tried quite a variety of off the shelf crystals, but above around 18MHz it becomes unreliable. Now, I could use the X2 function and a 12 MHz crystal to get to the normal 24MHz speed, but it worries me that a 24MHz crystal has problems booting when the device is rated for a 24 MHz clock.

A 5pF load seems really low to me, especially when most crystals present between a 16pF and 20pF load. This seems like a big mistake to me, but maybe I'm missing the big picture. I know that Atmel claims it was due to reducing the power consumption, but this seems like a bad tradeoff.

I have completely removed and loading caps from the circuit and the problem still exists. My PCB traces from the crystal to the pins are less than .5" and on a blank PCB, present less than 2pF (limits of the meter) of a load. I initially was using a socket, and had thought that the added capacitance of the socket may be an issue, but the problem still exists after soldering in the 24MHz crystal. VCC on the chip is 5VDC. I've tried crystals from ICM, ECS, Citizen, and generic ones with both series and parallel loading. All of the crystals work great with an AT89S8252.

Have any of you had a similar problem? Any word from Atmel on this? Thanks in advance and sorry for the long post, but I wanted to give as much info as possible.

Trev