|
<< Click to Display Table of Contents >>
Commands in IEC 870-5-101 and 104 Slave Protocol |
Block Tag to handle select or execute commands in IEC 870-5-101 and 104 Slave protocols
Option |
Description |
|---|---|
Protocols |
IEC 870-5-101 Slave Unbalanced, IEC 870-5-101 Slave Balanced, and IEC 870-5-104 Slave |
Numerical Parameters |
B1: Station number, B2: 4 (four, data reading of cache memory), B3: ASDU (from 45 to 51 and from 58 to 64, please check the next table), and B4: Object address |
Parameters in String format |
Not available |
Block size |
Four Elements |
Writing |
Sends to the Master an answer to a Select or Execute command |
Reading |
Receives Select or Execute commands sent by the Master |
The meaning of possible values for the B3 (ASDUs) parameter are described on the next table.
Possible values for ASDUs
Value |
Name |
Description |
|---|---|---|
45 |
C_SC_NA_1 |
Single command |
46 |
C_DC_NA_1 |
Double command |
47 |
C_RC_NA_1 |
Regulating step command |
48 |
C_SE_NA_1 |
Set point command, normalized value |
49 |
C_SE_NB_1 |
Set point command, scaled value |
50 |
C_SE_NC_1 |
Set point command, short floating point number |
51 |
C_BO_NA_1 |
Bitstream of 32 bits |
58 |
C_SC_TA_1 |
Single command with 7-octet timestamp |
59 |
C_DC_TA_1 |
Double command with 7-octet timestamp |
60 |
C_RC_TA_1 |
Regulating step command with 7-octet timestamp |
61 |
C_SE_TA_1 |
Set point command, normalized value with 7-octet timestamp |
62 |
C_SE_TB_1 |
Set point command, scaled value with 7-octet timestamp |
63 |
C_SE_TC_1 |
Set point command, short floating point number with 7-octet timestamp |
64 |
C_BO_TA_1 |
Bitstream of 32 bits with 7-octet timestamp |
When a Driver receives one of the commands described previously, this Block Tag receives a block with information about that command. On this Block Tag's OnRead event, the application must handle the received information, changing the Block Elements and writing that block back to the Driver. This way, the Driver can send an answer to the Master. The Elements of this Block Tag are the following:
•Element 0: Command value, depending on the type of command
•Element 1: Cause of Transmission, 6: Activate or 8: Deactivate
•Element 2: 1: Select or 0: Execute
•Element 3: Quality of Command, 0: Undefined, 1: Short pulse duration, 2: Long duration pulse, or 3: Persistent output
When an indication of an activation command is received, that is, Element 1 (one) equal to 6 (six), the application must respond immediately with a positive ACTCON (Activation Confirmation) command if the command can proceed, that is, Element 1 (one) equal to 7 (seven), or a negative ACTCON command if the command cannot proceed, that is, Element 1 (one) equal to 135.
If a positive ACTCON command is sent, the application must then check Element 2 (two, Select or Execute) and execute the proper action.
If an Execute command is requested, the application must execute the command and, after finished, send an ACTTERM (Activation Termination) command to indicate that the command was executed, that is, Element 1 (one) equal to 10.
The next example contains an OnRead event for this Block Tag.
' CMDIndication is a Block Tag with size 4
' This Tag's parameters are the following
' AdviseType = 0 (AlwaysInAdvise)
' AllowRead = True
' AllowWrite = False
' B1 = <station address>
' B2 = 4
' B3 = 45 to 51, 58 to 64
' B4 = <command point address>
' EnableDeadband = False
' Size = 4
Sub CMDIndication_OnRead()
Dim CMD, SE, COT, QU
CMD = Item(1).Value ' Command value
COT = Item(2).Value ' COT
SE = Item(3).Value ' 1=Select, 0=Execute
QU = Item(4).Value ' Quality of command
Select Case COT
Case 6
' ACT(6) must be answered with ACTCON(7)
WriteEx Array(CMD, 7, SE, QU), TimeStamp
If SE = 0 Then
' Execute the command here, probably
' a writing to another Driver
' Sends an ACTTERM(10)
WriteEx Array(CMD, 10, SE, QU), TimeStamp
End If
Case 8
' DEACT(8) must be answered with DEACTCON(9)
WriteEx Array(CMD, 9, SE, QU), TimeStamp
End Select
End Sub