Sys tick timer

[lpcware]

Content originally posted in LPCWare by mcu_programmer on Fri May 28 10:40:25 MST 2010
I have noticed that the systick timer on LPC1111 is decremented by full clockspeed rather that half clock speed (as it says in user manual docuement). The CMSIS has SYSTICKCLKDIV in SYSCON that is not docuemented. Is there some late change that has happened that is not yet documented?

Is it possible to confirm this?

[lpcware]

Content originally posted in LPCWare by curtvm on Sat May 29 08:07:09 MST 2010
I have the Rev. 00.10 manual, which does not have the /2 info.

That matches my hardware.

Its either one or the other, and I believe what my scope is telling me. If you look at the revision history on the manual, it appears they have a problem getting their story straight on the systick timer.

(It is a little disturbing that it appears to be that hard to get the correct info into the user manual for such a simple part of the micro. They make the chip, so it shouldn't be that difficult. I can imagine a scenario where someone ran a 'test' on the systick timer, toggling a pin on each systick irq, only to 'discover' that the freq readout says half of what they think it should be, and therefore conclude (incorrectly) the systick timer must be 'half' of the system clock. That's my bet.)

[lpcware]

Content originally posted in LPCWare by mcu_programmer on Sat May 29 05:39:01 MST 2010
In the user manual UM10398, rev 00.12, page 210 it says,

"Clocked internally by a dedicated system tick timer clock. The system tick timer clock is fixed to half the frequency of the system clock."

[lpcware]

Content originally posted in LPCWare by curtvm on Sat May 29 03:35:24 MST 2010
The user manual says-

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Quote:
Clocked internally by a dedicated system tick timer clock with the same frequency as the ARM core clock (system clock).

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So, it should be decremented at 'full speed'.

I just tested the systick timer on a lpc1114 to be sure I had it working correctly- system clock 48mhz, reload val 47999, produced a 1ms irq (verified with scope). I also tried changing the 'SYSTICKCLKDIV' register while debugging, and it makes no difference (and it shouldn't, as it doesn't exist in the 11xx).

I looks like an error in the LPC11xx.h header file (referring to a non-existent register). The13xx series use that register, and have another clock source option for the systick timer which the M0 do not.