marshalllester

MC9S12E128CFUE will not oscillate with pierce

Discussion created by marshalllester on Sep 13, 2012
Latest reply on Sep 17, 2012 by marshalllester

MC9S12E128CFUE will not oscillate with pierce

 

1) used pierce osc for 5 years on older controller pcb

2) designed new pcb with some optoisolator changes and other component changes - 2 layer

3) OCS and PLL layout unchanged

4) OCS and PLL layout unchanged exactly as specified in data sheet

5) PE7 XCLKS tied directly to VSS to select pierce osc

6) xtal is ECS 8mhz Part # ECS-80-20-4

7) 22pf caps 1.0 mohm in parallel no RS series resistor

8) tried many different xtals and caps - no success

9) tried 3 different batches of processors for DigiKey Mouser and Arrow with no success

10) checked every power supply and ground pin

11) made sure VDD1 and VDD2 are connected to only decoupling caps and nothing else

12) lifted all pins except DBUG, VDD and VSS pins and OSC and PLL pins so they are connected to NOTHING - no success

13) built new 4 layer PCB and tested as above - no success

14) I was told OSC needs NO program to run correctly and should see correct OSC on oscilloscope - nothing

15) on one pcb the OSC signal would appear around 4Vpp for 30 sec then drop to 2VPP for 30 sec then drop out entirely

16) mask sets used are all: 0M06C

 

 

GSC PCB.jpg

 

GSC SCEMATIC_Page_1.jpg

Outcomes