RS-232 Setup

All the settings here should just explain themselves,

• Port if a * appears next to the port, and it is not the current port, that port is in use by another application.
• Baud rate , it is possible to select a baud rate not supported by your UART, typically nothing over 115K except if you have the hardware.
• parity, data and stop bits The modbus default is 8E1, and 8N1 on some newer devices.
• RTS control this allows U to tell the driver the RTS line must be: always on, off or toggle, which is the default setting.
• Responsiveness default = 0. A delay in milliseconds (approximate to within 20) that is instituted before sending a response to any valid or invalid frame.
• Load register values... like it says.
• Units are off.. this puts all stations as off-line initially, so U have to turn each one on.
• Perform MOSCAD checks this one helps testing for a Motorolla MOSCAD/Mostrac radio-telemetry unit, then just rejects all requests which would just end up reading "empty" data from one of those units, and returns a exception code to warn the master.

RS232 wirring

Use this layout below to translate 9-25-pin connectors on your PC and DTE equipment.

9 pin	25 pin	Signal name
1	8	CD (Carrier detect)
2	3	RX (Receive Data)
3	2	TX (Transmit Data)
4	20	DTR (Data Terminal Ready)
5	7	SG (Signal Ground)
6	6	DSR (Data Set Ready)
7	4	RTS (Request to Send)
8	5	CTS (Clear to Send)
9	22	RI (Ring Indicator)

A 9-pin wirring diagram looks like this...

3----------3
2----------2
5----------5

The handshake control lines can also be looped back. This is easiest done by putting a blob of solder between 2 adjacent pins or using a very short piece of insulated wire between the 2 pins that must be looped. Translate the pin #s below for a 9-pin connector.

4+
 |
5+

6 +
  |
8 +
  |
20+

RS 232 hints

When in a RS-232 protocol, (P.S. nothing stops you using 422/485 via a converter) the comms screen shows a running dump of stuff sent/recieved. use the show timestamps tick-box to show timing information.

This screen now also shown the 3 incomming modem control line states, both through 3 indicators, and then also in the list-box view whenever a line-state changes.

Loops are sometimes needed by the device, for instance DTR output normally drives the DSR/DTR input on a device (your modem if it is an older one with millions of lights has it) modems are DCE (Data communication equipment), and this means the pins do not correspond to the pin convention above, but in fact are opposite.

Using a modem with this simulator does work, and even 232/485 converters. The slave (recieving) side of a dial-up will not auto-answer however, U need to put the modem into auto-answer and suppress the modem connect messages yourself using AT codes.