Applies To:
  • CitectSCADA 1.00 1.01 1.10 1.11 1.20 2.00 2.01 3.00

How do I test the serial port and driver? 

Use the loop back tester. The serial drivers PCxI, MCxI, COMxI or COMx may be used.

Configure a unit for each port to be tested. There should be no other drivers configured. Each port will transmit a frame of random length. This process is repeated when the entire frame is received.

I/O Devices form
Name: User supplied unique name
Number: Network wide I/O device number
Address: Not used
Protocol: LOOPBACK
Port name: Use the "Port name" from the Ports form

Citect.ini option

LoopBack = 0
Set loop back to 1 if internal loop back is to be performed (make sure this entry is deleted after running the loop back test), otherwise a loop back connector which ties pins 2 and 3 together is required at each port. The COMx driver does not support internal loop back.

Size = 512
Set the maximum frame size to 'size'. The length of each frame transmitted is random between 1 to size - 1. The default size is 512.

Special Statistics

Use "page driver" in the kernel page to look at the statistics. Type 'v' to set to verbose mode. The following counters are used:

  • Number of characters transmitted.
  • Number of frames transmitted.
  • Number of characters received.
  • Elapsed time in milliseconds.
  • Characters received per second.
  • Start time in milliseconds.
  • Total number of errors (Should be 0)
  • Error code of last error.


  • LOOPBACK.DLL Loop Back Driver for windows

Error Code

6 The received character is not the same as the character transmitted.