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

How do I use the Transmitton protocol? 

The serial drivers PCxI, MCxI, COMxI or COMx may be used. The Ports form should be set up for 9600 baud, 8 data bits, odd parity and 1 stop bit.
I/O Devices form
Name: User supplied unique name
Number: Network wide I/O device number
Address: Not used
Protocol: TXMITTON
Port name: Use the "Port name" from the Ports form

Citect.ini option

MaxVar = 21
Number of real outstation variables.

ReqDelay = 0
Do not delay responses to CITECT.

PollFreq = 8
Do one background poll for every eight consecutive ACK received. A smaller value may cause unnecessary polls.

Standard citect.ini options

MaxPending = 1
Block = 40 bytes
Retry = 3
Delay = 0
TimeOut = 10000 milliseconds
PollTime = 0
WatchTime = 10 seconds


  • TXMITTON.DLL - The TRANSMITTON driver for windows
  • TXMITTON.DBF - The TRANSMITTON variable template


Vs:b Analog values (Byte)
Vs:b.d Digital status (Bit)
Cs:c Channel status (Bit)
s Outstation number, 1-28
:b Byte number, 0 to 31
:c Channel number, 1-248
.d Bit address, 0-7
Special Variables
Vs:0.0 is the Isolated Flag.
Channels Cs:1 to Cs:248 are the same as Vs:1.0 to Vs:31.7
Analogue 1 to 8 are the same as Vs:8 to Vs:15
Vs:21 to Vs:31 are not outstation data they only exist only in the driver, they can be used to store temporary data.