Lpc2000

I'm confused by what you have said but here's what I think I know:  
RTCK is pulled high on the board.  No problem.

To enter and use JTAG debug, DBGSEL must be pulled high.  It is 
normally held low by a pull down resistor.  Install the jumper to 
use JTAG.  The BSL jumper doesn't matter during JTAG operation.

This is the way it is described in James Lynch's tutorial on page 
7.  And, other than issues with OCDRemote, it worked for me when I 
first tried using JTAG.  Do to a limited number of pins, I am not 
currently using it.


Richard

--- In lpc2000@yahoogroups.com, "frank_kienast" <fkienast@v...> 
wrote:
>
> I have an Olimex LPC2106 header board.  I was not having any luck 
> getting this to communicate with an LPT port debugger, so I did a 
> few tests.  
> 
> According to the LPC2106 datasheet (Section 18 - EmbeddedICE 
logic), 
> both the DBGSEL and RTCK pins must be held high on reset to enter 
> debugging mode.  However, the document with the header board from 
> Olimex says that DBGSEL should be held low during power up to 
enable 
> debug mode, and it doesn't mention RTCK at all.  I tried all 4 
> combinations of logic on these two pins, using both reset and 
> removing and re-applying power.  Regardless, I always found that 
TDO 
> is floating.  If I'm understanding correctly, it should be either 
> high or low at all times in debug mode since it is the JTAG data 
> output.  
> 
> To eliminate possible parallel port issues, I used another 
> microcontroller to attempt to communicate with the JTAG port for 
> testing purposes.  As expected, I found that TDO remains floating 
> throughout all attempts at communication.  Next I tried 
configuring 
> the secondary JTAG pins via a short program.  When I do this, I 
find 
> that TDO (using the secondary port) assumes a strong high or low 
> state, which changes during communication.  Looking at a JTAG 
state 
> diagram and doing a bit of bit twiddling, I found I was able to 
get 
> into Shift-DR mode on the JTAG port.  I was able to read the 
device 
> ID (I got 0x4F1F0F0F).  However, attempts to write the IR did not 
> work.  Regardless what I wrote to IR I would get the device ID 
back 
> when I read data in from DR.
> 
> I know my circuit is good, given that I can communicate manually 
via 
> the secondary JTAG port (in a limited fashion, which may be due my 
> incomplete understanding of the JTAG protocol).  Why won't the 
> primary JTAG port work at all?
> 
> I remember once reading that some people had problems getting the 
> primary JTAG port to work with a different LPC2* chip (I don't 
> remember which chip but it was not the 2106).  The Olimex board 
has 
> a 14.7456MHz crystal (which I can't change).  Could that be part 
of 
> my problem?
> 
> Incidentally, I noted that a sample "LED flash" program continued 
> running happily throughout all my tests (even where I was 
> communicating actively with the secondary JTAG port).  Is this 
> normal?  
> 
> Thanks for any help.
> 
> Frank
>