Verifying RS-485 with a TimeTap
The TimeTap (Model 8178T or 8179T) is a good troubleshooting device to determine if RS- 485 data is present. If a TimeTap is installed on the line, or if you have an available TimeTap, connect it to the RS-485 bus per the instruction manual. Connect the TimeTap directly to a PC running either HyperTerminal or Procomm, using the baud rate setting of the Master Clock and 8 bit, No start bit, 1 stop bit and flow control set to hardware (Note that HyperTerminal requires you to do a "Call" and "Disconnect" then a "Call" and "Connect" or "Call" and "Call" before the new baud rate and settings are used). A readable ASCII data stream should be shown on the monitor every second. If the data is present and readable every second, the RS-485 output of the Master Clock and the wiring to that point is ok. If it is showing unreadable characters, the RS-485 + and - Data lines are backwards and if it isn't present at all, either the RS-485 signal is bad or there is a PC setup issue.
To verify a Model 8178T TimeTap or 8179T TimeTap has a proper output:
- Connect the TimeTap into the serial port of a laptop computer. A standard DB9 to DB25 adapter may be required with an 8178T TimeTap.
- Using the terminal emulator screen, you should see a line on your screen every second that looks similar to one of the three samples below (Depends on the selected Data Format).
- 306 13:23 STZ=05 (Data Format 0)
- THU 11NOV99 13:23:36 (Data Format 1)
- 99 315 18:36:14.267S (Data Format 2)
Note: If there is a "?" or "*" at the beginning of the line, the Master Clock is not time synced. Contact Spectracom Customer Service for assistance.