Technical data of CPU 31x 
  7.7 CPU 317-2 PN/DP 
CPU 31xC and CPU 31x, Technical data 
Manual, Edition 08/2004, A5E00105475-05 
7-35 
Technical data 
Analog channels  4096/4096 
of those local  256/256 
Assembly 
Racks  Max. 4 
Modules per rack  8 
Number of DP masters 
•  Integrated 
1 
•  via CP 
2 
Number of function modules and communication processors you can operate 
•  FM 
Max. 8 
•  CP (PtP) 
Max. 8 
•  CP (LAN) 
Max. 10 
Time-of-day 
Real-time clock  Yes (hardware clock) 
•  Factory setting 
DT#1994-01-01-00:00:00 
•  Buffered 
Yes 
•  Buffered period 
Typically 6 weeks (at an ambient temperature of 
104 °F) 
•  Behavior of the clock on expiration of the 
buffered period 
The clock keeps running, continuing at the time-
of-day it had when power was switched off. 
•  Behavior of the realtime clock after POWER 
ON 
The clock continues running after POWER OFF. 
•  Accuracy 
Deviation per day: < 10 s 
Operating hours counter  4 
•  Number 
0 to 3 
•  Value range 
2 
31
 hours 
(if SFC 101 is used) 
•  Granularity 
1 hour 
•  Retentive 
yes; must be manually restarted after every 
restart 
Clock synchronization  Yes 
•  In the PLC 
Master/slave 
•  On MPI 
Master/slave 
S7 signaling functions 
Number of stations that can be logged on for 
signaling functions 
32 
(depends on the number of connections 
configured for PG / OP and S7 basic 
communication) 
Process diagnostics messages  Yes  
•  Simultaneously enabled interrupt S blocks 
60 
Testing and commissioning functions 
Status/control variables  Yes  
•  Variables 
Inputs, outputs, memory bits, DBs, timers, 
counters