Lpc2000

I am experiencing some problems with chaining an LPC2138 and LPC2106 on 
JTAG.  The BDI2000 intermittantly has trouble synchronizing the chain 
and takes several attempts before it "locks".  I am wondering about the 
way that I did the chaining and welcome any comments.

What I did was to take the TCK, TMS, TRST & RESET signals and ran them 
from the JTAG header to each processor (in parallel).  The data signals 
I ran in a daisy chain:
    JTAG.tdo --> LPC2138.tdi
    LPC2138.tdo --> LPC2106.tdi
    LPC2106.tdo --> JTAG.tdi

This does work, but about 20% of the time I get synchronization problems 
where the BDI2000 reports a problem reading the ICE BREAKER registers.  
After 2 to 5 successive retries it will link.  In severe situations, I 
have to power cycle the target board to achieve a link.

Once linked, it stays linked.  Rarely (I don't recall but may have 
happened) while debugging will it lose the synchronization and have to 
re-initialize.

Has anyone experienced this?  Is the wiring of multiple JTAG ports as I 
described?  Do I, or should I, consider using the RTCK signal?

Regards,

TomW


-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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