Technical data

Table Of Contents
SFBs for Compact CPUs
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
28-59
Instance DB
The SFB SERVE_RK operates in combination with an instance DB. The DB
number is passed on with the call. Access to the data in the instance DB is not
allowed.
How to Use Connection Memory Bits
You can lock or enable SEND and FETCH jobs of your communication partner via
connection memory bit. Thus, you can prevent overwriting or reading of data that
have not been processed yet.
You can specify a connection memory bit for every job.
Connection memory bit
DB100
MB100
L_CF_BYT
L_CF_BIT
L_TYPE = DB
L_DBNO
L_OFFSET
SERVE_RK
Data access can be locked
via the connection memory
bits TRUE/FALSE!
SEND_RK
FETCH_RK
R_CF_BYT
R_CF_BIT
R_TYPE = DB
R_DBNO
R_OFFSET
R_CF_BYT
R_CF_BIT
R_TYPE = DB
R_DBNO
R_OFFSET
A
ssignment of
the memory
bit to the DB
Uses memory bit for writing to the DB
MB200
Connection memory
DB101
DB102
DB103
Uses memory bit to read the DB!
Communication partner
Y
our CPU
7 6 5 4 3 2 1 0