Modem: 8 bits/character and Even or Odd parity


Jorge Saenz

New Member

The serial number of my modem (56k ZOOM/FAX MODEM EXTERNAL)


I´m sending commands to the modem via a particular software.
When I configure the serial port of the PC at 9600,Even parity,7 bits and 1 bit of stop the modem sends me a "0" as responses of the commands.
If I configure the serial port as (9600,None,8,1) there is no problem too.
When I configure the serial port as (9600, Odd, 8, 1) if I send the command ATL0 to the modem it respondes me with a "?B".
And when I configure the serial port of the PC as (9600,Even,8,1) if I send a command to the modem it doesn´t respond nothing, and it doesn´t make the action indicated by the command. I´ve tried with the HyperTerminal of Windows and with this configuration it doesn´t work well, but with the others there´s no problem.

1 - Is it necessary to configure the modem in a special way in order to work with 9600 bps, Even or Odd parity, 8 bits/character, 1 bit of stop.?
2- The modem takes this information of the serial port, doesn´t it ?
3- Why the others configuration works well and only the especificated two fails down ?

Thanks and Regards




New Member
Hey jorge,

First. I am far from being well versed with that issue, just have been utilizing the i-net for +10 years & throughout that time have read numerous posts from others about ZOOM modems & subsequent replies from other who do know. Me try to learn. :)

Zoom modem are extremely fickle modems. So, I would suspect that since 8-N-1 is the setup required by the greatest majority of modem users, the software writers most likely focused on ensuring that setup functioned properly. It's been quite some time since I've seen a connection that required anything other. CompuServe ini used 7-E-1, but even they saw that they were in a minority & changed.
I would try to find the site that provides their drivers & hope for the best.
Anyway, after reading about endless problems with ZOOM modems, I ldecided to avoid any modem whose name begins with a "Z." :) Not exactly scientific, but..
Another idea. Is there an option that will enable you to force the modem to connect at a certain speed? The code that enables 56K is pretty tight, so combine that with the fickleness of Zoom modems & the "gate for failing" due to an error is widened. Forcing the modem to bypass the drivers for 56K *might* be of help. Hey, without a force range/speed, it will access those drivers eventhough they won't ultimately be utilized.

Sorry couldn't offer more than opinions & guesses. Have a good day!