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6.2.4
Global Control (Sync, Freeze, Clear Data)
Description
The global control frame is an SDN frame with 2 bytes of net data from the DP
master with SSAP = 62 to SAP 58 of the DP slave. As a DP slave, the SPC 4-2
can only evaluate this frame if the DP controller is in the "Data Exchange" state. In
all other states (for example Wait-PRM, Wait-Config), SAP 58 must be deactivated
by the FLC with Request-SA = 7FH. A Global-Control frame (GCT) would then be
rejected with "No-Service-Activated (RS)".
In the "Data Exchange" DP status, the following settings must be made in SAP 58
of the SPC 4-2:
Buffer-available > 0
Request-SA = Station address of DP master
Request-SSAP = SSAP (different from DEFAULT-SAP)
Access-Value = {01H, 02H, 03H}
Reply-Update-Ptr / SDN-/DDB-Tln-Tab-Ptr = don't care
Buffer available is not decremented in the control byte of SAP 58. . A global control
frame with a net data length other than 2 is not evaluated by the SPC 4-2 if
"Check-GCT-Length-Off = 0" is set in mode register 2.
If "Check-GCT-Length-Off = 1" is set, monitoring of the net data length of a global
control frame is deactivated.
The global control function allows a special control command to be sent to one
(single), several (multi), or all (broadcast) DP slaves. The data format of the two
data bytes is shown in the table below.
Address
7
6
Byte 0
Res
Res
Byte 1
Sele
Sele
ct7
ct6
PROFIBUS Controller SPC 4®-2 LF
C79000-G8976-C157-3
Bit Position
5
4
3
Sync
Unsync
Free
ze
Sele
Select4
Sele
ct5
ct3
2
1
0
Unfreeze
Clear
Res
_Dat
a
Select2
Sele
Sele
ct1
ct0
DP Interface
Meaning
Control-
Command
Group-Select
59
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