SDL-News: real-time simul. and time on microcontroller

Subject: SDL-News: real-time simul. and time on microcontroller
Date: Sun Feb 23 2003 - 18:07:49 GMT

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Hi Scott,

There is no standard SDL statement returning the time unit.

To do real-time simulation :

 - in ObjectGeode : real-time simulation is not available,
   the time is discretized. If you set a 10000 time units
   timer - SET(NOW+1000, T1) - you will not wait for 10000
   seconds or milliseconds or etc. to see the timeout.

 - in Tau SDL Suite Simulator : real-time simulation is
   available, the time unit is seconds on Windows.

 - other tools : I have not tried.

Concerning code generation for a target, the time unit
depends on the tool used and on the target. Here is an example
for a Motorola 68HC11 microcontroller, with C code generated
using ObjectGeode for bare systems (i.e. having no executive
on the target) code generation (my board has 32 kilobytes of
RAM and ROM):

A code fragment I wrote manually to get the current time
value (in seconds) in hc11second, by counting the
long hc11second;

##pragma interrupt_handler RtiInt
void RtiInt()
{ static int tictac = 0;
        if (++tictac >= 400){ /* for 12 MHz */
                tictac = 0;
        TFLG2 |= 0x40;

##pragma abs_address:0xFFF0
void (*rtiint_vector)() = RtiInt ;
##pragma end_abs_address

In lib/g2_com.h (file in the ObjectGeode library), I replaced
"time" with "hc11second" in :

     extern long hc11second;
     ##define G2T_NOW() \
         ((GX_TIME_T)(hc11second / GX_TIMER_SCALE))

Then in the SDL model, the time unit is 1 second.

Naturally, you do not have to write such code for targets such
as VxWorks, win32 etc. where a clock is available.

Tau SDL Suite code generators (C Advanced or C Micro) provide
similar features.

Laurent Doldi.

At 10:09 21/02/2003 -0800, you wrote:
Hi all:
Sorry I didn't know my approach is specific to the tool and host that I use.
questions. I need to do real-time (realistic) simulation on my SDL design,
so is there any way in SDL I can know the time unit being used if I switch
tools or host systems? It sounds like that different tool/host will give me
different forms of NOW, in different time unit, when I run a real-time
Regards, and thanks for all the comments,

Laurent DOLDI
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