Hello everyone, i'm new to the forums, and i'm a new pronto pro installer.

I'll go straight to the point. I have a hardware, which i want to control over a serial interface, a Marantz PMD570 solid state recorder. The problem is that the pmd570 requires hardware handshaking with the rs232's CTS and RTS lines, and as i get it, the RFX9600 doesen't provide the handshaking (only three rs232 lines).

So, i want to ask you if any of you ever encountered a problem as this one and has found a solution (not using the problematic hardware is not an option here :) ). I would like to know if anyone knows if there are some products that enable the transition from rs232 without handshaking to rs232 with handshaking. If i will not find another solution I will make one of my own with a microcontroller, but i want to avoid this option if possible.

Cant you loop cts to rts or do i have the wrong end of the stick

Yeah i think this is the case. The sender must first rise one of the two (cant remeber now which one CTS or RTS), then the pmd570 replies with lifting the other one, and after this it's ready to receive data.

What xrmichael is suggesting is correct. On the Marantz side, tie RTS and CTS together so when ever it asserts RTS it sees CTS as asserted. Another approach is to always have CTS (an input) on the marantz side tied to a pin that should always be asserted in a true RS232 system. Such a Pin is DTR which should be asserted whenever the equipment (Marantz) is operational.

I tried with the bridging but it didnt work. Here's what the manual says:

1. The host requests data by setting RTS to L.
2. Upon data request by CTS, the PMD570 responds
by setting RTS to H if not busy.
3. The host checks if CTS is H and stats data output
on TxD.
4. When data output finishes, the host sets RTS to H.
5. The PMD570 checks if CTS is H and sets RTS to L.

The host is the RFX9600. This might be why the bridging didn't work. The Marantz waits for the RFX9600 to lower it's RTS and then reacts.

Hmm as i look this list now it doesen't really make sense. I have to investigate this further.

I would be doubtful that you'd make this work for RFX9600 but I am not the expert on 232 cables.

if you connect pins 7,8 together on the device you should beable to get around the issue.

Unfortunatelly it doesen't help. The problem is that the host (eg. RFX9600) must set the RTS line, requesting data, not vice-versa.

Here is a decent reference for pinouts and meanings

[Link: interfacebus.com]

The provided explanation of RTS must be read in the context of a modem (a Data Set). The device raises it to the modem (it is an output from the device (Data Terminal) to the modem (Data Set). The description in the reference is poor in that it does not consistently talk about a single entiry e.g. the connector on the device (Data terminal).

In Null Modem work CTS may also be used to control transmission. If held asserted, then the device may transmit freely. If controlled the device may transmit only when CTS is asserted. This then becomes the crux of the matter when there is no modem. How does one control CTS at the distant End from the near End? RTS, a controllable output signal on a good implementation may be used to act as CTS at the other end. In this case a 5 wire cable is needed with RTS crossed over to CTS just as Tx is crossed over to Rx. The real secret of dealing with RS232 cables and modems/null modems is understanding what is supposed (according to the specs) to be going on.

In RS232 work (but of course Marantz or Phgilips may not be obeying the RS232 protocols) RTS and CTS are the pin pair that are used to control transmission, sometimes called "flow control". RTS is an output signal (on either side of the cable). No device should ever look at RTS to make a decision. It asserts RTS when it wants to send data (RTS=Request To Send). CTS is the pin that is always an input. Its meaning when asserted is that the device is being told that it is okay to transmit. That is why tying RTS and CTS together on one side of the cable should satisfy the RTS/CTS signaling protocol. Doing this does eliminate flow control and the receiving device must be able to receive data at any time no matter how busy they are.

A terminal device may not always be ready to receive data. If that is the case some sort of flow control is needed. Flow control is performed by controlling the transmission of data, not its reception. Flow control is initiated by the receiving side and obeyed by the transmitting side.

The two other pins of interest are DCD (DCD-Data Carrer Detected) and DSR (DSR=Data Set Ready). They are inputs to a device. DSR says the data set, the modem, is ready for operation, and the DCD signal says that a carrier has been detected by the data set (modem) so data may be forthcoming. In three wire work a device should assume DTR and DSR are always asserted as there is no modem.

IMHO a well engineered serial device will supply on one of the pins (normally DTR) a signal that is always asserted as long as the unit is powered up and the interface is ready to receive data. This signal can then be used at the other end to satisfy DSR and DCD.

What you are describing is interesting. My understanding is that the Philips RFX devices only use three pins of the DB9 connector (2,3,5) and no other pins contain voltage or signal. Bear in mind that I do not own or use any RFX devices, so I am talking only theory. In theory, theory and practice are pretty close, In practice they are not.

Hope that helps explain it.

BArry thanks for the help. I've also come over the things you mention in the post over the last days. True, the RFX9600 serial extender uses only the TX, RX and GND pins, no others. But the MArantz needs an external device to set a line to which it listens so it gets ready to recieve the data. Unfortunatelly the RFX9600 isn't capable of setting that line.

To make things more complicated, the MArants in itself too doesent use all of the rs232 pins but only Tx, Rx, CTS, RTS and GND. So there is no DCD or DSR pins used, so i can't use them to provide the necessary RTS.

I will soon start working on a small interface which transforms philips's 3 pin communication to a 5 pin communication with the flow control. Currently i'm looking for a small footprint microcontroller that will have all the necessary periphery.

Anyway, thank you very much for your help.

Edit, i found something new. Seems that Marantz implemented an older version of the rs232 protocol, which goes like this:

Old RTS/CTS handshaking is different

What is confusing is that there is the original use of RTS where it means about the opposite of the previous explanation above. This original meaning is: I Request To Send to you. This request was intended to be sent from a terminal (or computer) to a modem which, if it decided to grant the request, would send back an asserted CTS from its CTS pin to the CTS pin of the computer: You are Cleared To Send to me. Note that in contrast to the modern RTS/CTS bi-directional flow control, this only protects the flow in one direction: from the computer (or terminal) to the modem.

For older terminals, RTS may have this meaning and goes high when the terminal has data to send out. The above use is a form of flow control since if the modem wants the computer to stop sending it drops CTS (connected to CTS at the computer) and the computer stops sending.

Which is the opposite of the modern Flow control. Strange decisions were made during the development of the device.

I am very surprised that looping RTS to CTS at the Marantz connector does not work. I would discuss it with Marantz tech support.

I just looked at their manual for the PMD570. IMHO they have completely misinterprested the use of RTS and CTS. they seem to want the host to signal them when it is okay to send data. Classically the Transmitting side inquires of the receiving side if it is okay to start a transmission. That is why the Line is called Request To Send. The signal requests permission to send (of the modem in a real link). The receiving end (the modem) would answer that they are cleared to send hence the signal name CTS.

The issue seems to be that the PMD570 expects the other side, the receiving side to Request them to send data. Maybe in china that is the way they do it, but not here or according to the RS232 specs. Since the RFX will never raise RTS, the PMF570 never sees its RTS (they use a straight through cable) go high. By spec they should not even be looking at it as RTS is an output not an input to a DTE (Data terminal equipment) like the PMD570.

In their timing diagram they actually show a cross over cable (7-8) but state they require a straight through cable.

I knew there was a reason I never bought anything from Marantz.

Just to let you know, if someone stumbles on the same problem. I solved the problem eventually...


... i bought a TASCAM SS-R1 solid state recorder and work like a charm. Thanks for the extensive help to all that contributed.