[TriLUG] C linux programming question

[Jeff Jackowski]

On Sat, 24 May 2003, Jim Ray wrote:

>Strictly speaking, PCs implement EIA-232.  RS-232 went bye bye many
>moons ago.  Many times, engineers will use something like a little Maxim
>IC to generate the +/- 12 V from a 5 V supply.

Well, if you want to get picky, I should have written EIA-574, but since
the RS/EIA difference is just a name change of the same organization, or
some kind of merger, they do get used interchangeably. From the
information I have found, EIA-232-D is just the slightly different
successor to RS-232-C. EIA-574 defines the 9-pin connectors used on PCs
and uses a subset of EIA-232-D on that connector. PCs have never, to my
knowledge, had a fully EIA-232 compilant interface. That would require a
25-pin connector (only one conductor is unused) and would provide
synchornous serial in addition to asynchronous serial.

BTW: TI makes several chips that are compatible with the MAX232 and 
similar offerings from Maxim, but are available for less, sometimes 1/3.

>> -----Original Message-----
>> From: Jeff Jackowski [mailto:jeffj1 at hiwaay.net] 
>> Sent: Saturday, May 24, 2003 5:55 PM
>> To: Triangle Linux Users Goup
>> Subject: Re: [TriLUG] C linux programming question
>> 
>> Actually, PCs implement RS-574, not RS-232. While they are 
>> very similar, RS-574 provides a 9-pin connector and defines a 
>> signal of 0 volts to be a logic 1. This allows a 
>> microcontroller running on 5 volts to send data directly to a 
>> PC serial port without any voltage level converter. It works 
>> quite well.

-- 
Jeff Jackowski
        http://ro.com/~jeffj/