Mapping of the Coupler Box
The signals of the Coupler Box and the connected expansion boxes are mapped in the order in which the hardware is connected.
For digital boxes always at least one byte is reserved.
If the boxes have less than 8 bits, the rest is filled with
zeros.
The data are represented with WORD alignment, i.e. for analog
modules the first WORD contains the status byte and an empty
byte.
Example: IE2301 4 digital inputs, 4 digital outputs, 8-bit input,
8-bit output; the first four bits 0-3 are assigned. Bits 4-7 are
not used.
Complex boxes are represented with input and output process image.
Example
IE3102, 4-channel analog input: per channel 1 byte control or status information, 1 empty byte, 2 bytes data.