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[DPRG] C Compiler

Subject: [DPRG] C Compiler
From: Rick J. Bickle rbickle at swbell.net
Date: Fri Aug 29 09:55:02 CDT 2003

Excellent, thanks Kip...

I have in fact selected the 22.1184 MHz crystal for baud rate
generation.

Do these timing figures take into account the address latch, or is the
address latch assumed to have a propogation time less than the address
setup time?

For RAM, is the read operation assumed to be faster than the write
operation and therefore used for speed calculations, or should we look
at both read and write, and use whichever has the fastest time?

Rick J. Bickle
Integrated Control Systems
Voice:  (972) 522-1593
Fax:    (972) 660-7950
Mail:   PO BOX 541058
        Grand Prairie, TX. 75054-1058
Email:  rbickle at intconsys.com 
Web:    www.intconsys.com


-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On Behalf
Of Kipton Moravec
Sent: Thursday, August 28, 2003 11:54 PM
To: DPRG List
Subject: RE: [DPRG] C Compiler


Page 28 of the XA Datasheet.
http://www.semiconductors.philips.com/acrobat/datasheets/XA-C3_5.pdf

For the flash memory:

(V3 * tc) - 36 ns

tc (ns) = 1/frequency

V3 depends on some wait state bits you can set but the values can be 2,
3, 4, 5

So if you have a 32MHz clock the flash should be faster than 26.5,
57.75, 
89, 120.25 ns depending on the wait states.
If you go with a 22.1184 MHz (good for baud rates) the flash should be 
faster than 54.4, 99.6, 144.8, 190.6 ns depending on wait states.


For data read

Worse case is
(V6 * tc) - 36 ns

V6 depends on wait states and valid values are 3, 4, 10, 11

So if you have a 32MHz clock the data SRAM should be faster than 57.75,
89, 
276.5, 307.75 ns depending on the wait states
If you go with a 22.1184 MHz (good baud rates) the data SRAM should be 
faster than 99.6, 144.8, 416, 461 ns depending on wait states.

Most SRAM are 45, 55, or 70 ns

Flash is all over but you can get 35, 45, 55 ns Flash.  Usually the
slower 
the cheaper.

That assumes no logic for decoding the memory.

Hope that helps
Kip


At 10:43 PM 8/28/03, you wrote:
>Rick:
>The limiting factor is not the uC clock speed. The memory spec times as
>follows:
>
>         access time from write enable to a memory cell plus hold time
>            on wite enable to ensure successful write
>         uC time from previous write to next byte fetched + time for
>            write enable. Function of uC clock speed and location of
>            data (internal cache, SRAM, EPROM, Flash, etc.)
>         data transfer method (bus, DMA, i2c, etc.)
>         Finally -- software. I haven't tracked this much at all, but
>            you can get an idea of the best speed by writing a
>            do-forever loop that generates a byte, writes it out, and
>            repeats. Assembly is fastest; I don't know enough to
>            comment.
>
>I'm sure there are more (Rodent?) but it has been years since I've done

>a worst-case analysis of this kind, and I'm sure there are memory 
>advancements I haven't heard of. These are the basics. With regard bus 
>speed, the memory parameters are more limiting that CPU times for 
>anything except cache RAM. Ralph
>
>On Thu, 28 Aug 2003, Rick J. Bickle wrote:
>
> > I was just investigating the details of flash memory. Anyone have 
> > any experience in handling flash memory? I was thinking of adding 
> > 256Kx8 of flash, and writing a loader program which would receive 
> > serial code data and load the flash in the system. This would 
> > increase my code space from 64K to 256K, and potentially make 
> > updating the firmware easier for the end user.
> >
> > Another question on another topic:
> >
> > Does anyone have a good definitive method for determining the 
> > necessary RAM or EPROM speed for a given clock speed of 
> > microcontroller? I have always done a rough calculation based on the

> > BUS speed for a given frequency, but am wondering if there is a 
> > better way.
> >
> > Thanks,
> > Rick J. Bickle
> > Integrated Control Systems
> > Voice:  (972) 522-1593
> > Fax:    (972) 660-7950
> > Mail:   PO BOX 541058
> >         Grand Prairie, TX. 75054-1058
> > Email:  rbickle at intconsys.com
> > Web:    www.intconsys.com
> >
> >
> > _______________________________________________
> > DPRGlist mailing list
> > DPRGlist at dprg.org http://nimon.ncc.com/mailman/listinfo/dprglist
> >
>
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