Lpc2000

volodymyr_tymchyshyn wrote:

>Hello,
>
>I am using Olimex "LPC-P2106" board with JTAG pins P0.17-P0.21
>(primary group).
>I prototype with LCD, so I need almost all pins set as "out" or "io".
>I there any trick to set pins P0.22-P0.30 (used for alternative JTAG
>and Trace) to output mode, while using the JTAG debugging?
>It looks like using them as "input" is not an issue (P0.31 is used for
>button on "LPC-P2106") but they do not switch to "output" in Debug
>mode. The JTAG shows the values of "direction" and "out" registers
>changing properly, but actual levels on pins look to remain "input"...
>
>  
>
I'm using the Secondary JTAG for debugging in my board and disabling the 
Primary JTAG for use as I/O.

Pins P0.27..P0.31 goto my JTAG unit, all other JTAG group signals are 
used for I/O.  There is no "interference" that I've seen.  You have to 
do two things to use the secondary JTAG: enable it and provide a startup 
delay.

To use the Secondary JTAG, I place the following into my crt0.S file:

================ begin crt0.S ==================
__undf: b     .                         // undefined
__swi:  b     .                         // SWI
__pabt: b     .                         // program abort
__dabt: b     .                         // data abort
__irq:  b     .                         // IRQ
__fiq:  b     .                         // FIQ
#endif

JTAG2:
   .word 0x55400000
PINSELREG:
   .word 0xe002c004

        .size _boot, . - _boot
        .endfunc


// Setup the operating mode & stack.
// ---------------------------------
        .global _start, start, _mainCRTStartup
        .func   _start
_start:
start:
_mainCRTStartup:

// Initialize Interrupt System
// - Set stack location for each mode
// - Leave in System Mode with Interrupts Disabled
// -----------------------------------------------
;
      ldr   r0, JTAG2
      ldr   r1, PINSELREG
      str   r0, [r1]       // activate secondary JTAG port.
;
      mov   r3, #0x10000
startdelay:
      subs  r3, r3, #1
      bne   startdelay     // give debugger time to catch us.
;
        ldr   r0,=_stack
        msr   CPSR_c,#MODE_UND|I_BIT|F_BIT // Undefined Instruction Mode
        mov   sp,r0
================ snip =======================


The above will turn off the Primary JTAG, turn on the Secondary JTAG and 
allow a delay for the JTAG pod to "catch" the processor. 

No, I do not believe that you can also use the Secondary JTAG pins as 
I/O AND use them for the JTAG functions at the same time...

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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