Siemens SINUMERIK Series Function Manual

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A4: Digital and analog NCK I/Os for SINUMERIK 840D sl1.2 Access via PLCExtended Functions50 Function Manual, 03/2013, 6FC5397-1BP40-3BA1Memory organization16 bytes (over all channels) are available for data exchange from and to the PLCrespectively. These areas have to be managed by the user (i.e. no overlapping of thevariables, not even across channel borders).The display of the variables within these areas depends on the setting in the machine data:MD10399 $MN_PLCIO_TYPE_REPRESENTATIONValue Meaning0 (default setting)System variables are displayed in little-endian format(i.e. least significant byte at least significant address)1 (PLC standard format, recommended)System variables are displayed in big-endian format(i.e. most significant byte at least significant address)Since big-endian format is generally the most common display type on the PLC (i.e. it alsoapplies to the PLC I/Os), it should normally be used.Note● The assignment of the input and output areas for direct PLC I/Os must satisfy thefollowing conditions:$A_PBB_IN[] ; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN])$A_PBW_IN[] ; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN] - 1)$A_PBD_IN[] ; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN] - 3)$A_PBR_IN[] ; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN] - 3)$A_PBB_OUT[] ; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT])$A_PBW_OUT[] ; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT] - 1)$A_PBD_OUT[] ; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT] - 3)$A_PBR_OUT[] ; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT] - 3)● The maximum number of bytes available for data exchange must not be exceeded.