05.91
1 General Overview
1.3.7 Command channel
1.3.7
Command channel
The PLC user program can trigger functions in the NC by means of the command channel,
whereby the user data for the functions are also transferred via this channel. A subsequent
Section describes the functions that can be initiated by means of the command channel.
The command channel is a high-speed data channel. The interface to the command channel
for the PLC user program is DB 41. The command channel is parameterized here and the
location of the user data is also specified (DB number, offset, length).
The command channel can process several jobs at the same time and is subdivided into user
interfaces (UIs) for this purpose. The system supports up to eight user interfaces, each of
them operating like an independent command channel. All the user interfaces are contained in
DB 41.
The PLC user program parameterizes the command channel and initiates processing by set-
ting a request bit. The PLC operating system then transfers the job contained in DB 41 to the
NC and subsequently stores the acknowledgement signals from the NC for the PLC user pro-
gram in DB 41.
The scope of the command channel can be specified by machine data:
Activate command channel:
MD 6026.1
Number of user interfaces:
MD 0033
Value range 0 to 8
Command channel
NC channel
Axis
Spindle
Command
channel
processing
PLC operating
system or FB
Command channel
User interfaces (UIs)
Link RAM
DB 41
DB
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NC
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PLC
Parameter
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Acknow-
ledge-
ments
Command
channel
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PLC
user
pro-
gram
User
data
UI 1
..
UI 8
© Siemens AG 1991 All Rights Reserved 6ZB5 410-0HE02
1–31
SINUMERIK 880 (PJ)
