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wek1
wek1
Associate
March 1, 2004
Question

uPSD UART Mode0 Max Baud

  • March 1, 2004
  • 8 replies
  • 1511 views
Posted on March 01, 2004 at 14:31

uPSD UART Mode0 Max Baud

This topic has been closed for replies.

8 replies

wek1
wek1Author
Associate
May 17, 2011
Posted on May 17, 2011 at 11:58

Hi,

The uPSD321x datasheet states (table 45) that the max. baud rate of UART in mode0 is 1MHz (constraining the Xtal freq. to 12MHz).

I haven't seen this kind of constraint in other '51 clones.

Is this true?

Have a nice day!

Jan
jinguanghua
jinguanghua
Associate II
May 17, 2011
Posted on May 17, 2011 at 11:58

I have tested Modeo using uart0, I got 1Mhz.

wek1
wek1Author
Associate
May 17, 2011
Posted on May 17, 2011 at 11:58

Yes, but what about the MAXIMUM baud rate?

Jan

sjo
sjo
Associate III
May 17, 2011
Posted on May 17, 2011 at 11:58

In uart mode0 the Baud rate is defined as Osc/12 and is fixed, as far as I am aware this has always been the case on 8051.

Regards

sjo
jinguanghua
jinguanghua
Associate II
May 17, 2011
Posted on May 17, 2011 at 11:58

I use 24M crystal on the board and uart 0 mode 0 mode, I got 2M speed.

wek1
wek1Author
Associate
May 17, 2011
Posted on May 17, 2011 at 11:58

I don't quite understand:

- what was the Xtal frequency? 12MHz?

- did you try higher Xtal frequency? and mode0 baud was still 1MHz?

Jan

wek1
wek1Author
Associate
May 17, 2011
Posted on May 17, 2011 at 11:58

Yes, of course, this is what I expected (as other '51 clones work this way).

But why then the ''max. 1MHz'' in datasheet of uPSD321x Table 45, page62?

Jan

PS. FrankJ, what is your device? Could you try it also @ 40MHz?

jinguanghua
jinguanghua
Associate II
May 17, 2011
Posted on May 17, 2011 at 11:58

ST3234A, I don't have 40Mhz crystal on hand.

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