ProSoft Technology 5204SE-MNET-PDPMV1 - Manual (Page 148)

5204SE-MNET-PDPMV1 ♦ ProLinx Gateway Reference
Modbus TCP/IP to PROFIBUS DP-V1 Pass-Through Master User Manual
Page 148 of 235
ProSoft Technology, Inc.
December 22, 2009
MNETDPV1_Inputs Variable - Quantum
This variable is an array of 1536 bytes. It is used to receive up to 768 words
(1536 bytes) of PROFIBUS cyclic input data from slaves on the PROFIBUS
network.
The order of data in this array will match the order in the PCB memory maps you
exported and/or printed. The following screen shot shows a typical memory map.
The PCB table lists usage in words rather than bytes, where one (1) word equals
two (2) bytes. In this example, there are only eight (8) total words or 16 total
bytes of PROFIBUS cyclic input data configured (highlighted in yellow) of the
available 1536 bytes that could be used. The 16 bytes (8 words) of PROFIBUS
inputs from the device assigned to Slave Address 1 will be stored in the first 16
bytes of this array.
You should also notice that the native storage size in the module's memory is 16-
bit or 2-byte word registers. If the number of inputs from the first configured
device is an odd number of bytes, you will see that memory register hold one
byte from the first device in its low-order byte. The higher-order byte of this
register will hold the first byte of data for the next configured slave device. In
other words, this data is byte-packed with no extra blank bytes inserted just so
the data for each slave address can begin on a low-order byte boundary.