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
PUT_E / GET_E 160 bytes does not exist
USEND_E / URCV_E 160 bytes does not exist
还有其他限制，看STEP 7帮助：Common Parameters of the SFBs/FBs and SFCs/FCs for S7 Communication