Highest Baud

Hello people
Does anyone know the highest Baud rate i can get with a
20mhz Xtal and 18F452 ?
the highest i can get using windows xp is 115200
i am using Max232


' Setup Hardware for uart
DEFINE HSER_BAUD 115200
DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 24h
DEFINE HSER_CLROERR 1

Synchronous... Datasheet... Table 16-3... 5Mb...

Asynchronous... Datasheet... Table 16-4... 312.5kb...

So thats clear would the problem be from my pc end then?

20Mhz isn't the greatest xtal frequency to produce high baud rates compatible with your PC without error... see item 3 from my reply on this thread...

http://www.picbasic.co.uk/forum/show...=&threadid=563

I always use DEFINE HSER_SPBRG instead of DEFINE HSER_BAUD. In some case, it appear to be more efficient

be sure of your DEFINE HSER_RCSTA and DEFINE HSER_TXSTA setting too.


regards

Thanks Mel
i have taken your advice on board and i have ordered a 22mhz
xtal.
but i think my problem is with my PC End
When i select any baud rate greater than 115200. i get a reply
from hyperthem that com1 not found

It is possible that Hyperterminal interrogates your PC's USART... I have XP-Pro SP2 on two four-month old 3.2Ghz desktop machines and a year old 2GHz Laptop... neither desktop lets me set a value higher than 115kb (the highest displayed), yet on the laptop, it permits setting right up to 920kb.

Hi!

Some useful links...


Regards

Luciano


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Terminal program:
(No setup, only one EXE file).

Terminal v1.9b 20040714.
http://bray.velenje.cx/avr/terminal/
(See custom baudrate).

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Does your PC need a high-speed serial port?
Take a look at:

http://www.comtrol.com

(RocketPort Plus PCI 2-port 98701-7)

RocketPort® Multiport Serial Controller Cards

The RocketPort's fully integrated, ASIC controller has superior throughput performance, reliability, and CPU utilization, making this price/performance leader ideal for data acquisition applications. Highlights include:

Optimum throughput performance up to 921 Kbps transmit and receive across all ports simultaneously.

Supports PCI 32- and 64-bit, 3.3 Volt, 5.0 Volt, PCI-X, CompactPCI slots and ISA bus architectures, ensuring compatibility regardless of the host environment.

Quick, easy installation using no interrupts or memory-mapping, freeing limited resources to support other hardware components/peripherals.

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