Siemens SINUMERIK 840D sl Function Manual page 51

MD10399 $MN_PLCIO_TYPE_REPRESENTATION
The logical PLC I/O addresses entered in the machine data and the number of bytes to be
transferred must be consistent with the PLC hardware configuration. In the configured areas,
there must not be any 'address gaps' in the PLC I/O expanded configuration.
Memory organization
16 bytes (over all channels) are available for data exchange from and to the PLC
respectively. These areas have to be managed by the user (that is, no overlapping of the
variables, not even across channel borders).
The variables within these areas are displayed either in little-endian (= 0) or big-endian (= 1)
format,
depending on the setting of the machine data:
MD10399 $MN_PLCIO_TYPE_REPRESENTATION
Since big-endian format is generally the most common display type on the PLC (that is, it
also applies to the PLC I/Os), it should normally be used.
Alignment
The assignment of the input and output areas for direct PLC I/Os must satisfy the following
conditions:
$A_PBB_IN[j]
$A_PBW_IN[j]
$A_PBD_IN[j]
$A_PBR_IN[j]
$A_PBB_OUT[k]
$A_PBW_OUT[k]
$A_PBD_OUT[k]
$A_PBR_OUT[k]
Furthermore, the maximum number of bytes available for data exchange must not be
exceeded.
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Little-/big-endian format display of system variables $A_PBx_OUT, $A_PBx_IN for PLC
I/Os that can be controlled directly from the NCK
value = 0 (Default)
System variables are displayed in little-endian format
(i.e., least significant byte at least significant address)
value = 1 (Standard format for PLC, recommended)
System variables are displayed in big-endian format
(i.e., most significant byte at least significant address)
; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN])
; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN] - 1)
; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN] - 3)
; j < ([MD10394 $MN_PLCIO_NUM_BYTES_IN] - 3)
; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT])
; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT] - 1)
; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT] - 3)
; k < ([MD10396 $MN_PLCIO_NUM_BYTES_OUT] - 3)
A4: Digital and analog NCK I/Os
1.2 NCK I/O via PLC
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