Applies To:
  • CitectSCADA x.x

How to setup the Square D SysLink PC/SyNet interface card. 


Square D Variables

Sw Register
w-b Digital
Vv Virtual Register
Vv-b Virtual Digital
w is the word number 1 to 32767
v is the word number 1 to 16000
b is the bit number 1 to 16

Digital, Int, Long, LongBCD, Real and String data types are supported.

Boards form
Board name: User supplied unique name for the board
Board type: SQUARED
Address: Board's memory start segment (in hexadecimal). 0xCA00 to 0xD300 (in 0x100 4K) increment.
I/O Port: Board's route number, it must be between 0 and 99
Interrupt: 2,3,4,5,6 or 7.
Special Opt: Specify the following network port parameters:
-b   Enable SY/LINK to receive broadcast messages from the network. The default is to disable broadcast.
-s   Set maximum network size to 100 instead of the default of 31.
-r  N Set the network baud rate. Where N is 0,1,2 or 3 for network baud rate of 62.5K, 125K, 250K and 500K respectively. The default is 500K.
Ports form
Port name: User supplied unique name for the port
Port number: not used
Board name: Use the "Board Name" from the Boards form.
Baud rate: *
Data bits: *
Stop bits: *
Parity: *
Special Opt: Special Opt Specify the following RS-422 port parameters
-b    Enable the RS-422 port to receive broadcast message from the network. The default is to disable broadcast.
-d   Prevent other network devices from communicating to the RS-422 port.
-n   Set the RS-422 port to Net-To-Net mode. The default is SY/MAX mode.
-p   Set the RS-422 port to Peripheral mode.
I/O Devices form
Name: User supplied unique name for the device
Number: Network wide I/O device number
Address: Address Route to the PLC. A blank route field means access to the registers on the SY/LINK card.
Protocol: SQUARED
Port name: Use the "Port Name" from the Ports form.

* The baud rate, data bits and parity specify the parameters of the RS-422 Port on the SY/LINK port.

Citect.ini options

MaxPending = 1
Block = 64 bytes
Retry = 1
Delay = 0
TimeOut = 2000 milliseconds
PollTime = 0
WatchTime = 30 seconds


  • SQUARED.DLL Square D SY/LINK Card Driver for windows
  • SQUARED.DBF Square D variable template

Virtual Mailbox Registers

  • Each square D card have 512 processor equivalent registers which can be read from and written to by PLC and Citect. By defining a unit with a blank address, that unit will behave like a PLC with 512 registers.
  • The virtual mailbox feature allows any square D I/O device to have its own 16,000 read only registers. Each PLC update these registers by writing to its own reserved area (Rreg) in the real mailbox registers in the following format:

W1: Number of registers in packet including this 3 register header.
W2: Citect I/O Device "Number".
W3: Start address of virtual register (1 to 16000)
W4 to W128: Data to go into virtual registers

  • The user can see a trace of each of these unsolicited data packet header by turning on debug error. i.e debug <portname> error. Each trace will be of the form:

<Date><Time> Unsolicited Mailbox(Rreg) Length(W1) Unit(W2) Reg(W3)

Special Statistic Counters

Receive Interrupts Hardware interrupts from card
Transmit Frames Frames transmitted
Receive Frames Frames received
Read Read requests from Citect
Block Read Read requests blocked into a single read
Unsolicited Unsolicited messages received
GetHeader Unsolicited messages with good header
GetData Unsolicited messages with good data
ReRead Card change flag register modified while processing current interrupt
Vread Virtual read requests from Citect
Bad Header Unsolicited messages with bad header
NoHeader Unsolicited messages with no header
BadData Unsolicited messages with inconsistent data
NoData Unsolicited messages with no data
Errors Errors detected
Last Error Last error code
Init Channel Number of INIT_CHANNEL from Citect
Init Unit Number of INIT_UNIT from Citect
Write Number of writes from Citect
VreadWait Increments every time the virtual registers are found to contain stale data. i.e data that have not being update in the last 30 seconds ([squared]Watchtime).