ColdFire/68K Microcontrollers and ProcessorsのトピックRe: MCF51QE128 - CPU speed

MCF51QE128 - CPU speed

Richard777 — Fri, 12 Oct 2007 00:29:52 GMT

Hi, I'm a MCF51QE128 beginner, I will be select a 16 Mhz Xtal like external oscilator, and I will be select the internal bus frecuency to 24 Mhz, with this values the frecuency of Core is 48 Mhz ?

Thanks in advance

--
Alban Edit: Please always include FSL Part Number in Message Subject line.
http://forums.freescale.com/freescale/board/message?board.id=FORUMUSE&message.id=865

Message Edited by Alban on 2007-10-15 11:57 AM

Re: MCF51QE128 - CPU speed

UK_CF_FAE — Fri, 19 Oct 2007 22:52:08 GMT

Hi Richard,

On the MCF51QE128 the instruction clock is the same frequency as the output from the ICS, and the bus clock (peripherals etc) is divided by 2.

Instruction clock = ICSCLK

Bus Clock = ICSCLK / 2

Device Reference Manual, PDF page 24. Figure 1-3

So, yes, if you use the 16MHz crystal, set the FLL to generate 48MHz, then the core will run at 48MHz and the peripherals at 24MHz.

I reckon

ICSC1_CLKS = 00

ICSC1_RDIV = 100

ICSC1_IREFS = 0

ICSC2_RANGE = 1

ICSSC_DRS = 10 (FLL factor is 1536)

This is going to give 48MHz exactly. Good luck

Mark

Re: MCF51QE128 - CPU speed

Richard777 — Sat, 20 Oct 2007 01:04:43 GMT

Alban sorry for my mistake and Mark a lot of thanks for your explanation

Bye