Lpc2000

--- In lpc2000@yahoogroups.com, "conhalk" <conhalk@y...> wrote:

> I am using the lpc2138, and I have wrote a program which includes 
> reading port0.16-24 pins at a 10 Mhz sampling rate:

[...]

> ON THE KEIL ARM SIMULATOR (60 MHZ) THE ROUTINE SAMPLES AT 10 Mhz.
> 
> ON THE REAL CHIP (60 MHZ) THE ROUTINE SAMPLES AT 5,5 Mhz ! ( I 
> specify the function to be copied to ram)	
> 
> Meanwhile, I use an output compare timer on a pin, and it works at 
> 10 Mhz both on the simulator and the chip (checked on a scope)!
> 
> The simulator shows the lDRB, STRB need 2,3 and the nop 1 cycle, 
> hence rate = 60 / (3+2+1) = 10Mhz
> 
> I guess LDRB, STRB actually take double time. If it is so, does 
> anybody know why? Is there any way around this?

The Keil simulator doesn't know about the waitstates that the MAM and 
AHB-to-VPB bridge add.  The simulator is not useful for simulating 
the timing of code involving jumps in flash and loads/stores to VPB 
peripherals.

See also http://groups.yahoo.com/group/lpc2000/message/7808

> Unfortunately I must use the 2138, and it has no external bus. Is
> it possible to achieve 10 Mhz sampling with this chip?

I don't think so.  It would with the new LPC214x or LPC210{1,2,3}.

Karl Olsen