Is there any documentation that talks about the necessity of
a crystal oscillator to make an LPC's JTAG work ??

LPC1768 in our case but I think I have run into this before on LPC2144.

I'd just like to know if someone knows where anything mentions
this requirement that for the JTAG to work, it would require a crystal
or some special PLL setup to work. i.e. internal RC oscillator doesn't seem to let the JTAG work.

Thanks,
boB

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On 23/07/2010 00:52, bobtransformer wrote:
> Is there any documentation that talks about the necessity of
> a crystal oscillator to make an LPC's JTAG work ??
>
> LPC1768 in our case but I think I have run into this before on LPC2144.
>
> I'd just like to know if someone knows where anything mentions
> this requirement that for the JTAG to work, it would require a crystal
> or some special PLL setup to work. i.e. internal RC oscillator doesn't seem to let the JTAG work.
I've always had a crystal on the chip when using JTAG with LPC2000
devices, but I've often used it with FPGAs which don't have a functional
crystal oscillator when the JTAG is operational, as well as MSP430 chips
with the internal RC oscillator.

Leon
--
Leon Heller
G1HSM
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Hi to all,

Maybe it is late but could be useful....
I've several part of LPC without an external crystal using Jlink as debugger and IAR as Toolchain.
The only modification I did is the .mac file in IAR where there is a couple of line codes for the Jlink debbuger....this file is recalled at each debug.

here is it:

execUserSetup()
{
// Disable the PLL.
__writeMemory32(0x00000000, 0xE01FC080, "Memory"); // PLLCON = 0
// Qualify the PLL change.
__writeMemory32(0x000000AA, 0xE01FC08C, "Memory"); // PLLFEED = 0xAA
__writeMemory32(0x00000055, 0xE01FC08C, "Memory"); // PLLFEED = 0x55

// Enable internal clock (LPC23xx only).
__writeMemory32(0x00000000, 0xE01FC1A0, "Memory"); // SCS.OSCEN = 0
// internal RC (LPC23xx only).
__writeMemory32(0x00000000, 0xE01FC10C, "Memory"); // CLKSRCSEL = 0

// Make sure that the flash memory system is correctly setup.
__writeMemory32(0x00000000, 0xE01FC000, "Memory"); // MAMCR = 0
__writeMemory32(0x00000007, 0xE01FC004, "Memory"); // MAMTIM = 7
__writeMemory32(0x00000002, 0xE01FC000, "Memory"); // MAMCR = 2

// If the MAM values was wrong, a dummy read is necessary to get the flash memory in sync.
__writeMemory32(0x00000001, 0xE01FC040, "Memory"); // MEMMAP = 1
__readMemory32(0x00000000, "Memory");
}

--- In l..., Leon Heller wrote:
>
> On 23/07/2010 00:52, bobtransformer wrote:
> >
> >
> > Is there any documentation that talks about the necessity of
> > a crystal oscillator to make an LPC's JTAG work ??
> >
> > LPC1768 in our case but I think I have run into this before on LPC2144.
> >
> > I'd just like to know if someone knows where anything mentions
> > this requirement that for the JTAG to work, it would require a crystal
> > or some special PLL setup to work. i.e. internal RC oscillator doesn't seem to let the JTAG work.
> I've always had a crystal on the chip when using JTAG with LPC2000
> devices, but I've often used it with FPGAs which don't have a functional
> crystal oscillator when the JTAG is operational, as well as MSP430 chips
> with the internal RC oscillator.
>
> Leon
> --
> Leon Heller
> G1HSM
>

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