by Jeff S Johans » Mon, 20 Feb 1995 22:52:09
Someone said I would need a faster chip, others said I do not.
I am looking into get that US Robotics 28.8K Sportster modem.
Thank you VERY much!
Jeff Johansen
by THE PIL » Tue, 21 Feb 1995 02:02:59
Yes you can. But do you really want to is the question. I once ran aQuote:>Can I use an external 28.8K modem with a serial port that uses a UART 8250
>chip?
>Someone said I would need a faster chip, others said I do not.
>I am looking into get that US Robotics 28.8K Sportster modem.
It will work, but problably not satifactory to what you want. If you are
forking out a couple of bills for a 28.8K modem, you want the performance
to be there.
To things to consider :
1) Do you use your modem with WINDOWS? If yes, you are definatly going
to want a 16550afn UART.
2) Do you do a lot of file transfers? If yes, you probably want to get
a 16550afn also.
So a simple answer?? If your going to invest the money for a good modem,
spend the money so that it can operate at top rates. Get the chip.
by Sam Winot » Wed, 22 Feb 1995 03:43:55
: Can I use an external 28.8K modem with a serial port that uses a UART 8250
: chip?
: Someone said I would need a faster chip, others said I do not.
: I am looking into get that US Robotics 28.8K Sportster modem.
: Thank you VERY much!
: Jeff Johansen
--
----
Name: Sam Winotai
1. Even/Odd Parity Problems w/ MV2700 & 8250 UART
I'm trying to send binary data out the /tyCo/1 serial port (at 57.6KB)
which is controlled by the 8250 UART on an 266 MHz MV2700 board. I need
to set the parity to even send a couple of bytes and then set the parity
odd for the remaining bytes which can range from a few to ~1000 bytes.
The problem that I've run into is that the 1st 2 bytes are correctly
sent in even parity and then the remaining odd parity bytes get sent,
but a few bytes have even parity. This problem goes away if I put a
taskDelay(1) call after a write() call of each byte.
One thing that I've tried which I thought would solve the problem but
didn't, was to make sure that all of the bytes are transmitted out of
the UART before I change parity from even to odd using a busy/wait loop.
This function, waitForTransmitterEmpty() is included below.
Both functions are adapted from i8250Sio.c in target\src\drv\sio &
i8250Sio.h in target\h\drv\sio
I realize that I'm doing something wrong, but I can't see it. Any
assistance would be greatly appreciated as I'm stuck on this problem.
Thanks,
-Jim
Here's the code that sets the parity:
void SerialTest::setParity( SerialTest::eParity _parity )
{
FAST int oldlevel;
char lcr = 0;
switch( _parity )
{
case PARITY_NONE:
lcr |= I8250_LCR_PDIS;
break;
case PARITY_ODD:
lcr |= (I8250_LCR_PEN);
break;
case PARITY_EVEN:
lcr |= (I8250_LCR_PEN | I8250_LCR_EPS);
break;
}
// always 8-bits, 1 stop bit
lcr |= (I8250_LCR_CS8 | I8250_LCR_1_STB);
oldlevel = intLock ();
SIO_CHAN *pChan = sysSerialChanGet(1);
I8250_CHAN *pI8250_chan = (I8250_CHAN *)pChan;
(*pI8250_chan->outByte) (pI8250_chan->lcr, lcr);
intUnlock (oldlevel);
Here's the waitForTransmitterEmpty() code.
void SerialTest::waitForTransmitterEmpty()
{
// wait until these bytes are sent before proceeding
SIO_CHAN *pChan = sysSerialChanGet(1);
I8250_CHAN *pI8250_chan = (I8250_CHAN *)pChan;
bool bBusy = true;
do
{
char pollStatus = ( *(pI8250_chan)->inByte) (pI8250_chan->lst);
if( pollStatus & (I8250_LSR_TEMT | I8250_LSR_THRE) )
{
bBusy = false;
}
}while( bBusy );
--
Jim Pisano
Senior Scientific Programmer
National Radio Astronomy Observatory
Central Development Lab
2015 Ivy Road, Charlottesville, VA 22903
804-296-0351
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