Siemens S7-300 appendix Technical data Data areas and their retentivity

Technical data of CPU 31x 7.4 CPU 315-2 DP

Technical data

Data areas and their retentivity

Flag bits		2048 bytes
•	Retentive memory	Yes
•	Default retentivity	MB0 to MB15
Clock flag bits		8 (1 byte per flag bit)
Data blocks
•	Number	1023
		(DB 1 to DB 1023)
•	Length	16 KB
Local data capacity		Max. 1024 bytes per task/510 per block
Blocks
Total		1024 (DBs, FCs, FBs)
		The maximum number of blocks that can be
		loaded may be reduced if you are using another
		MMC.
OBs		See the Instruction List
•	Length	16 KB
Nesting depth
•	Per priority class	8
• additional within an error OB		4
FBs		See the Instruction List
•	Number	2048
		(FB 0 to FB 2047)
•	Length	16 KB
FCs		See the Instruction List
•	Number	2048
		(FC 0 to FC 2047)
•	Length	16 KB
Address areas (I/O)
Total I/O address area		max. 2048 bytes/2048 bytes
		(can be freely addressed)
Distributed		Max. 2000
I/O process image		128/128
Digital channels		Max. 16384
of those local		Max. 1024
Analog channels		Max. 1024
of those local		Max. 256
Assembly
Racks		Max. 4
Modules per rack		8
Number of DP masters
•	Integrated	1
•	via CP	1

7-14	CPU 31xC and CPU 31x, Technical data
	Manual, Edition 08/2004, A5E00105475-05