Hi Art,
RS422 and RS485 are multi-drop serial buses. This means that multiple senders
could conceivably be transmitting characters at the same time. In practice,
the devices take turns transmitting, but this requires that each device must be
able to shut off its' driver circuitry when idle. I believe that it is typical
to use the RTS output of the handshake circuit to turn the transmit driver off
and on automatically.
The RS485 line will have some way to control the enable/disable of the driver
circuit.
Mike
-----Original Message-----
>From: Art <>
>Sent: Aug 23, 2006 12:47 PM
>To:
>Subject: [ts-7000] Re: rs232 vs rs485
>
>Yan
>
>Thanks for the quick responce. The question I was asking was intent
>on getting some information on a com port that has the ability to run
>rs485 vs a com port that can just run rs232. I have a TS-7200 with
>rs485 capable port. I have it setup to run rs232. I am running
>rs232 on the other end. I have hardware and software flow control
>disabled on both ends. Yet it seems to stop sending/receving. But
>what I was asking is for the diffrences in hardware on the ts-7200
>for just rs232 vs (rs232 and rs485) on a com port. I get the same
>software to run fine on COM1 vs COM2(get's stuck).
>
>--- In "Yan Seiner" <> wrote:
>>
>> --- In "Art" <kingartjr@> wrote:
>> >
>> > Is there any diffrences in a rs485 configured port that would
>prevent
>> > it from functioning as a standard rs232 port? I then ask what
>are the
>> > diffrences? it seems event when I turn the flow control off on
>this
>> > port it still functions as if it were in place. Getty doesn't
>seem to
>> > work well on com2.
>> >
>> rs232c and rs485 specify different electrical standards. I am not
>> sure what you are asking.
>>
>> Typically rs485 is run on 2 or 4 wires, with no flow control lines.
>> I'm not that familiar with the 4 wire setup; I've only used
>> half-duplex (2 wire). Each station turns its transmitter on when it
>> wants to say something; the other stations are supposed to respect
>> that and not transmit.
>>
>> RS232c is point-to-point, and provides for all sorts of redundancy
>> (the full spec has secondary RX and TX lines, even...) There are
>> liens that each station is supposed to turn on and off when it is
>> ready. There are also signal lines for special events like carrier
>> detect.
>>
>> Basically, RS232c was designed to talk short distances to a modem,
>an
>> RS485 was designed to talk long distances to multiple peers. Also,
>> an RS485 bus is (I believe) a voltage differential setup, whereas
>> RS232 is referenced to 0, but I could be getting confused with
>another
>> bus I am working with...
>>
>> So when you switch a port from rs232 to rs485, you lose all hardware
>> flow control, since there is none.
>>
>> --Yan
>>
>
>
>
>
>
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