Technical data

Table Of Contents
S7 Communication
System Software for S7-300/400 System and Standard Functions - Volume 2/2
21-4
A5E00739858-01
The guaranteed minimum size of the user data for an SFB/FB with 1–4 variables is
listed in the following table:
Block Partner: S7-300 Partner: S7-400
PUT / GET 160 bytes 400 bytes
USEND / URCV 160 bytes 440 bytes
BSEND / BRCV 32768/65534 bytes 65534 bytes
Further information on the user data size can be found in the technical data of the
respective CPU.
Exact User Data Size
If the user data size specified above is insufficient you can determine the maximum
byte length of the user data as follows:
1. First read the data block size valid for communication from the following table:
Own CPU Remote CPU Data block size in bytes
S7-300 Any 240 (S7-300)
S7-400 S7-300 / C7-300 240 (S7-400)
S7-400 S7-400 or CPU 318 480
8. Use this value in the following table to read the maximum possible user data
length in bytes. It applies for an even lengths of the areas SD_i, RD_i, ADDR_i.
Number of used parameters SD_i, RD_i, ADDR_i
Data block
size
SFB/FB 1 2 3 4
240 (S7-300) PUT/GET/
USEND
160 - - -
240 (S7-300
via integrated
interface)
PUT 212 - - -
GET 222 - - -
USEND 212 - - -
240 (S7-400) PUT 212 196 180 164
GET 222 218 214 210
USEND 212 - - -
480 PUT 452 436 420 404
GET 462 458 454 450
USEND 452 448 444 440
960 PUT 932 916 900 884
GET 942 938 934 930
USEND 932 928 924 920