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From: "Steven Levine" 
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@Date: Thu, 04 Dec 2003 10:38:22 -0800
Subject: Re: Contacting Ray Guinn
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In , on 12/04/03 
   at 12:21 PM, "Randy Fowler (personal)"
 said:

Hi,

>It's odd that the "software multiplier" is calculated
differently between
>the  two drivers... 

Actually, I'm not at all surprised.  If neither driver knows about this
board's clock multiplier method so the results from each driver are, by
definition, undefined.

>...typical serial ports allow higher transfer rates than the  standard
>COM1/2 on the computer. This is done by doubling the external  clock
>given to the serial port. In the case of our cards the factor is  eight,
>i.e. the maximum speed is 921600 baud (115200 x 8).  When the driver does
>not know about this factor of eight, the  configured speed is wrong.

The last sentence is the key.

Here's some the code I use to program the baud rate on some systems:

  /* Baud rate divisor = 1,843,200 / (Baud Rate * 16) */
  #define ACE_B2D(Rate)	((unsigned short)(1843200L/((long)Rate<<4)))

   cDivisor = ACE_B2D( cBaud );		/* Calc baud rate divisor */
  _disable();				/* Disable interrupts */
  /* Set baud rate */
  outp( iAddr + ACE_LCR, bLCRMsk | ACE_LCBRENB );
  outp( iAddr + ACE_BRLSB, cDivisor );
  outp( iAddr + ACE_BRMSB, cDivisor >> 8 );
  outp( iAddr + ACE_LCR, bLCRMsk );	/* Initialize LCR */

This code would have very similar problems to what you are seeing.  By
design, it does not reprogram the multipler so it's probably limited to
450K baud, although I've never needed to run a port that fast on this
system.

>I do not know why SIO2k does not compensate it. This driver is designed 
>to check the real port speed when the port is first opened.

You are misinterpreting what "check the real port speed" means.

>So it  should see the real factor of eight, and compensate for it.

Why?  You are assuming the code is prescient and knows how to operate
boards is was not designed to operate.  My code is typical.  When it was
written there was no way to reprogram the multiplier.  I'd have to check,
but I probably don't even have the port definitions defined to access the
multiplier.

>As of late yesterday, we decided to abandon further attempts to get this 
>board working and have decided to try a different board that has a jumper
> to allow setting the clock speed multiplier manually from 1x up to 8x. 
>They  suspect that this would solve the problem with the two drivers.

Probably.  I would suspect this model exists to overcome the problem where
the drivers can't be modified to support the different hardware.

BTW, did they mention which UART chipset they use?  I might as well see
what's really needed to run one of these beasts.

Regards,

Steven


-- 
----------------------------------------------------------------------
"Steven Levine"   MR2/ICE 2.41
#10183 Warp4/FP15/14.093c_W4
www.scoug.com irc.webbnet.info irc.fyrelizard.org #scoug (Wed 7pm PST)
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