Siemens SINUMERIK 840Di Function Manual page 1143

Data transfer from PLC to NC, with data read via synchronized actions;
Byte 1 serves as the semaphore
ID=2 WHENEVER $A_DBB[1] == 1 DO $R1 = $A_DBR[12] $A_DBB[1] = 0
2. Read word of position offset 8 without semaphore and store in MW 104:
CALL FC 21 (
Function
5: Update control signals to channel:
The purpose of function 5 is to transmit important control signals at high speed in between
cyclic data transfers. Data bytes 6 and 7 of user interfaces DB21 to DB30 are transferred to
the NC. The channel is specified in parameter "IVAR1". This enable, for example, the feed
disable, read-in disable to be transferred outside of the PLC cycle.
The following signals are relevant:
Signal
Enable
Funct
S7Var
IVAR1
Error
ErrCode
Power Line Basic PLC Program (P3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Enable :=
Funct :=
S7Var :=
IVAR1 :=
IVAR2 :=
Error :=
ErrCode :=
I/O Type
I Bool
I Byte
I Any
I Int
Q Bool
Q Int
M 10.0,
B#16#3,
P#M 104.0 WORD 1,
8,
-1,
M 10.1,
MW12);
Value range Remarks
1= FC 21 active
5 5: Control signals to channel
S7 data storage area Not used
1. Max. channel Channel number
1: "Funct" invalid
10: Channel no. invalid
Detailed description
2.12 Block descriptions
// if True, FC 21
is active
//Read data
2-231