Re: [N8VEM: 14609] SBC V2 build not working

[opticpow <wa...@ingram.net.au>]

Hi Doug,

I've posted pics to here

I've got the scope out and done some probing. I've uploaded some scope captures with the board pic above.

• I have CPU & UART clock
• Flash A0 is pulsing at 1mhz
• CPU reset is at 4.5v. should this be at 5v?
• CPU IORQ is high
  
• CPU MREQ is pulsing @4hmz
• CPU WAIT & BUSRQ are both at 3.9v. Should this be 5v??
• while reset button is pressed, RESET drops to 200mv
• Flash CE is pulsing between about 2.5v & 5v @ 4mhz (see pic). Not sure this is right??
  
• Flash OE is pulsing at 2mhz
• RAM A0 pulsing @ 1mhz

Where abouts do I find the short loop images. I've had a browse on the files section and could not find them.

Thanks,

Wayne.

On Monday, September 10, 2012 8:14:29 AM UTC+10, douglas_goodall wrote:

Wayne,

Here are a few steps I follow. (Some of which you have already done...)

1. Verify power on all +5 pins

2. make sure CPU oscillator is wiggling

3. Make sure clock input to CPU is wiggling

4. Make sure A0 on the flash is wiggling, maybe CE and OE as well

5. Make sure clock input to UART is wiggling

6. See if Tx pin on UART is wiggling after reset, if so serial wiring is likely the problem

7. Use low level test images with short loops (also known as scope loops)

8. When doing low level probing , if a signal is not doing what you expect you may have a problem

where the socket pin does go into the hole, but for some reason solder hasn't reached it, reflow it and check again

(test for continuity between chip lean and trace underneath the board. I have found some of these).

It is possible to have a bad chip. The bottom line if following the basic functions...

CPU clock is running, EEPROM is reading (if not maybe problem with I/O decoder) Check enabled on I/O devices

These are my major thoughts. Be brave, we have all been through this difficult moment and most have working boards now.

You learn a lot in this phase if you engage it enthusiastically.

Regards,

Douglas