Asynchronous,Synchronous and Interface Standards..

[mngeow]

I want to know for both cases of Asynchronous and Synchronous, are they considered Simplex,Half duplex or full duplex? Or is it possible they both async and sync support all those methods?

Also,for the RS232,RS423,RS422,RS485,I would like to know for each of these interface standards,which of the following apply to them,async,sync,simplex,half duplex or full duplex.

Sorry if my question is abit unclear I'm not really sure how to phrase it myself.

Thanks for the help! =)

 

[Sceadwian]

Synchronous or not, simplex means communication is only available in one direction EVER. Half means that one side OR the other can communicate, full means both sides can communicate at the same time.

 

[BrownOut]

I'll just give you a hint: RS232 is asynchronous, full duplex.

 

[Sceadwian]

RS232 standards do not require bi-directionality. Two wire RS232 can meet RS232 standards and be half duplex.

 

[KeepItSimpleStupid]

Synchonous means in sync with something. That something is usually a clock.

 

[BrownOut]

The most complete implementation of RS232, and most used is full-duplex operation. Virtually every RS232 serial port ever sold was full-duplex.

 

[Sceadwian]

That's a really fuzzy area there BrownOut, there are a LOT of RS232 standards unfortunately, I personally haven't even been able to find a proper copy of any fully issued standards based RS232 spec... ever! Got any links you could provide? It's been a pet peeve of mine, as it's the most non-standard standard that exists.

 

[BrownOut]

The current standard is TIA-232-F (1997) I do not have a copy. There is a charge for getting it. I do, however, have the military Tactical Data Link - B standard... somewhere. ( military version of RS232 and V.24 )

Back to the question; anyone who has interfaced a peripheal to the standard computer serial port has seen an example of an asynchronous, full-duplex communication channel. Typically, the interface is RS232 ( or, any of the similar standards ) If you've designed and built your own peripeals, then you've certainly studied this port in detail. Now, if you can tell why it's asynchronous and full-duplex, then you should be able to analyze the other types of ports for those parameters.

 

[Sceadwian]

I have BrownOut, there are no standard connectors for any RS232 standard I've found, only specification for one side being male or female. The use of DE9 and DB25 connectors is traditional, not a part of any standards based specification I have been able to find. Nor is there any requirements I'm aware of for it being full duplex, again based on standards, which I've been unable to find! The most detailed description I have ever seen of any RS-232 spec is electrical only. -3 +3 is the logic threshold. +/- 12 volt tolerant if not a bit more, short circuit tolerant, and some capacitance/resistance limits which basically come down to transmission line specs, the most commonly referenced one I can find is 20k baud is considered the physical limit. Those again though are probably from parasitic values.. Even if bidirectionallity is required software flow control can do that over two wires.

I'm really curious to see some hard links that define RS-232C standard Even TIA-232-F would be wondrous as that's based on EIA-232C which is as close as I've come to and that has no description of connectors and that's only from hearsay of the standard as you said I can't download the whole thing.

 

[KeepItSimpleStupid]

Protocal is not specified, but the connector, pin assignments levels are. See: https://en.wikipedia.org/wiki/Rs232

Way back when, it was an interface between DTE and DCE's. The DCE was provided by the telephone company. All sorts of things were possible, I believe. There was a loopback test that essentially tested the analog loop and there were signals available to give you logic 1 and logic 0.

I do remember a high speed modem that used the low bandwidth channel to provide the ACK and NAK responses required.

Once the IBM PC came out, the standards went out the window. Manufactures seemed not to even understand the standard at all. CTS, RTS, DTE, DCE were almost always messed up in just about every way possible. You needed a breakout box to get anything to talk to each other.

I do remember the ASR33 Teletype and the current loop interface.

The IBM Selectric was a Half Duplex serial interface at 134.5 BAUD. The ASR33 may have been half-Duplex too, I can't remember. I do remember entering passwords on something that created a black area where things overtyped on something.

 

[mngeow]

Thanks for all the replies guys. I roughly understand about the RS-232 now . I'll try and apply what I've learnt to the rest. Thanks again!

 

[BrownOut]

I have BrownOut, there are no standard connectors for any RS232 standard I've found, only specification for one side being male or female. The use of DE9 and DB25 connectors is traditional, not a part of any standards based specification I have been able to find.

Just because you haven't found a specification does not mean the connector is not part of a specification. Since you've not read the spec, then you don't know that it isn't specified. Guessing doesn't prove a thing.

Nor is there any requirements I'm aware of for it being full duplex, again based on standards, which I've been unable to find!

So since you havent' found a spec, it doesn't exist? The DB-25 port is based on the spec, but even if you don't believe it, it does not change what I've claimed that if you have developed peripheals for the standard serial port, such as the many RS232 products available, then you've studied the parameters I've claimed. No amount of speculation about what's in the spec or what's not changes my claim.

Protocal is not specified, but the connector, pin assignments levels are. See:

I agree, just from my experience around RS232 for the last 25 years.

 

[Sceadwian]

Brownout regardless of any opinion or experience if you can't refrence the standard then weasre both just guessing. I really would like to see the specs myself Google turns up surprisingly no direct links to a standard that I can find and several million pages of vague refrences. I know what's commonly used I just find it funny such a standard can't be found.

 

[BrownOut]

You're inabliity to find the spec is not a concern of mine. If you have something to say about the intelligence I post, then you should be able to reference it. It's not my job to prove you right or wrong.

 

[KeepItSimpleStupid]

Since RS232 is a Standard, it MUST BE PURCHASED: **broken link removed**

It's just they way it is.

 

[BrownOut]

I tried to say that back in post #8:

The current standard is TIA-232-F (1997) I do not have a copy. There is a charge for getting it.

 

[MrAl]

I have BrownOut, there are no standard connectors for any RS232 standard I've found, only specification for one side being male or female. The use of DE9 and DB25 connectors is traditional, not a part of any standards based specification I have been able to find. Nor is there any requirements I'm aware of for it being full duplex, again based on standards, which I've been unable to find! The most detailed description I have ever seen of any RS-232 spec is electrical only. -3 +3 is the logic threshold. +/- 12 volt tolerant if not a bit more, short circuit tolerant, and some capacitance/resistance limits which basically come down to transmission line specs, the most commonly referenced one I can find is 20k baud is considered the physical limit. Those again though are probably from parasitic values.. Even if bidirectionallity is required software flow control can do that over two wires.

I'm really curious to see some hard links that define RS-232C standard Even TIA-232-F would be wondrous as that's based on EIA-232C which is as close as I've come to and that has no description of connectors and that's only from hearsay of the standard as you said I can't download the whole thing.

Hi,

Some motherboards include a RS232 header but no DB type connector. I guess it's up to the user to supply a matching header connector, cable, and DB connector for more common usage.
Even some manufacturers of devices dont go by the standard and use lower voltage signals for the ports. Some devices that work in more standard RS232 ports dont work in those lower standard ports, but they still make them that way.