All Forums
 Hardware
 Ethernet, IR, Serial, CAN and high speed data
 Baud Rate offset due to Clock
 Forum Locked
 Send Topic to a Friend
 Printer Friendly
Author Topic  

vcsdesigns

0 Posts

Posted - 06 Oct 2006 :  20:58:26  Show Profile  Email Poster
I am aware that the PXA255 uses a 14.7456 Mhz clock and divides it down to get the baud rate/bps.

However, this division is rarely perfect.

Can you tell me the actual rate of the 115,200 baud setting on the BitsyXB board?

akidder

1519 Posts

Posted - 07 Oct 2006 :  08:30:59  Show Profile  Email Poster
The BitsyXb uses a 13.000 MHz clock on the PXA270 (see section 6.3.10 of the user manual), resulting in a 115.044 kbps bit rate. That's an 0.14% error, which translates to an 1.4% over the usual ten bits (8,N,1). Most UARTS sample each bit 16 times, which allows for up to 6% error before even one of the samples fails.

Here are a few other baud rates and their bit rate error using a 13 MHz clock:
9.6k: 9.6012 (+0.01%)
19.2k: 19.202 (+0.01%)
38.4k: 38.348 (-0.1%)
115.2k: 115.044 (-0.1%)

On ADS PXA255 products (BitsyX, VGX, GCX and others), we use a 3.6864 MHz core clock, which divides evenly down to the common serial baud rates (9600, 19.2k, 38.4k, 115.2 kbps).
Go to Top of Page
  Topic  
 Forum Locked
 Send Topic to a Friend
 Printer Friendly
Jump To:
Eurotech Support Forums © Eurotech Inc. Go To Top Of Page
This page was generated in 0.02 seconds. Snitz Forums 2000