on 1/17/00 2:15 PM, Daniel Senderowicz at daniel@synchrods.synchrods.COM
wrote:

> Chris,
> 
>> Yep, that'll do it. If you feel like terminating it, you need a BNC "T"
>> and two 50 ohm terminators.
> 
> This machine has one of those multipin connectors (10base2?) in
> the back of my 5000/240. So probably I'll have to find a
> terminator for those.

  Sorry about my boneheadedness, I misread and thought you were using a BNC
network. As was mentioned, if you have a loopback connector or a transceiver
that allows you to force a link, you can use that. My Allied Telesyn AUI ->
10Base-T has a switch to force the link on even if it isn't connected. As
was also mentioned, there isn't really any need to do this as long as you
don't set the interface up.

> I'm not sure I understand the concept of having a "set" speed in
> the serial ports. In port 2 I have the modem, in port 3 I have a
> little box that converts serial to parallel so I can drive my
> stylus epson printer. So if only the modem is working and the
> printer isn't or viceversa, then we always have a case in whicn
> they don't work at the same speed, am I wrong? In fact the
> little box seems to choke above 19200, while the modem works at
> 115200, but it stalles sometimes probably because of the
> handshaking. Thanks for your help.
> 
> Dan
> 
> 

    It goes like this: 115200 is the speed at which the modem can
communicate with YOUR computer, this speed in modem-speak is the DTE. (short
for Data Terminal Equipment)
    The impression I get from the DEC manuals is that the DZ serial chip
cannot transmit or receive information any faster than 38400. Keep in mind
that the fastest modem at the time was the US Robotics HST/V.42. (which
incidently has a top DTE of 38400) Since your modem can communicate with the
computer its attached to at 115200, you'll have to set it back to 38400 or
else flow control won't kick in. (I highly recommend RTS/CTS over XON/XOFF)
    It might also be helpful to disable MNP5 compression, and disable
receive flow control. (ACK/ENK based usually, I don't think NetBSD supports,
nor needs it) Also keep in mind that you need a properly wired RS-232C
connection for RTS/CTS handshaking to work. As a side note, the reason the
test routine may be complaining is that it's expecting your modem to be
using XON/XOFF when it isn't (and shouldn't be).
    The DEC docs seem to say this:

One Port, Two Port, Status

>= 9600, >=9600, OK
>= 9600, 19200, OK
>= 9600, 38400, OK
>= 19200, 19200, OK
>= 19200, 38400, Not OK
>= 38400, 38400, OK

or vice versa. 

    I could give you the techno-speak lowdown on why this is (supposedly)
true, but in the PC world it's like trying to use a 56k modem on an 8550
UART as opposed to a 16550 UART. The reason your modem stalls is probably
that the DZ buffers are overrun and it has to retransmit at a slower speed.
Even if your link speed is only 14.4k, I've seen my HST push beyond 4k/sec.
More than the DZ can handle. Setting the DTE to 38400 or 19200 instead of
115200 should fix that. Hope that helps.

    Chris