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Conference mvblab::sable

Title:	SABLE SYSTEM PUBLIC DISCUSSION

Moderator:	COSMIC::PETERSON

Created:	Mon Jan 11 1993
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2614
Total number of notes:	10244

2539.0. "3rd party serial boards" by METMV3::COX () Thu Feb 27 1997 15:02

    I have a customer with a need for 2 serial ports for data input. They
    have to use one for the console, so they went to the Digiboard product.
    to give them the needed 2 ports.
    
    These systems (21 of them) are going to be used for Air Traffic
    Control in Germany. There is a 10ms time limit to respond to incoming
    messages. The ports that ship with the 2100 can respond in 1-4ms. The
    Digiboard is in the 30-40ms range. 
    
    The customer has been trying different eisa serial boards using the
    standard UNIX ace driver with mixed results. Currently they have a
    board from Blackbox with 2 16550 uarts. The board performs well except
    for some buffer/silo overruns. 
    
    The question is...is there any other serial port cards that will work
    with UNIX or is there anyway to tweak the driver or kernal to stop the
    overrun errors. 
    
    BTW... they are running V3.2d, but they get they same overrun errors on
    V4.0
    
    Thanks 
    Tom Cox
    Sales Support

T.R	Title	User	Personal Name	Date	Lines
2539.1		LEFTY::CWILLIAMS	CD or not CD, that's the question	`Thu Feb 27 1997 17:19`	8
	Why do they need one for the console? Is there a reason a graphics console won't work? Given the latency of the onboard ports, that sounds like a better solution... C
2539.2		NETRIX::"[email protected]"	paradis	`Fri Feb 28 1997 09:15`	24
	A possible reason for the difference in timing between the on board ports and the Digiboard ports is that data has to pass trought the concentrator and eisa adapter before being delivered to the streams driver. I would expect the eisa com cards to perform as well probably even better than the two on board serial ports. As far as the overrun errors are concerned the only possible solution would be to either lower the baud rate or find out what activity on the system is causing the delaying of the interrupt from reaching the serial driver. The UNIX serial driver sets the interrupt trigger level to 1 byte. That means that at anytime a byte is stored in the FIFO an interrupt will be issued. Once the driver's ISR is entered we process all data that is in the FIFO. The 16550 has a 16 byte FIFO so that means that some subsystem on the 2100 is holding the IPL long enough for the 16550's buffer to fill up. The only way around this is to determine what is running on the system that is causing the delay or try a lower baud rate. --dennis [Posted by WWW Notes gateway]
2539.3	Support for console port	METMV3::COX		`Fri Feb 28 1997 10:48`	6
	Thanks for the answers so far. >.1 They need to use one of the serial ports as the console port for remote console support. >.2 I will suggest they lower the baud rate and see what happens.