serial communication using HART modem

[gore]

When using a HART modem on COM1 the HART modem generates a 1200 Hz signal (which corresponds to a low or 0-level) during reading (no writing done at all!) from the serial port. This 1200 Hz signal on the HART bus interferes with the communication making reading not possible. Is the TxD signal set to 0 during initialisation or reading from the COM port? System: Windows NT, LabView 4.01

[JR_A.]

I'm not exactly clear on how the 1200 Hz interferes or where it is. HART is actually a protocol that can be used on rs232. LabVIEW doesn't directly support the HART protocol but there is an alliance company that has developed a LabVIEW driver for the HART protocol. Here is their info:

CARDIAC
P.O. Box 4290
N-7002 Trondheim
Norway
Attn: Robert Almaas
Tel: +47 73 82 52 00
Fax: +47 73 82 52 22
Email: cardiac@cardiac.no
WWW: http://www.cardiac.no

But the TxD line is used to transmit data and the setting of it during a read should not affect the read operation. Hope this was helpful.

JR A.
Application Engineer
National Instruments
http://www.ni.com/ask

[gore]

Thank you very much for the information. I'll visit the cardiac site.

Kind regards,

F. Huijsmans