505-6108A | Siemens Analog Input Module

The Analog Input module operates asynchronously with the controller. Thatis, the controller and module do not update at the same time. Instead, the module translates all analog inputs in one module update and stores the translated words in buffer memory. When the controller I/O scan starts, it retrieves the words from the buffer memory of the module The PPX:505–6108A analog signal is translated into a 12-bit digital word. Since the controller requires a 16-bit word for inputs, the 12-bit value from the converter is placed into a 16-bit word for transmittal to the controller. As shown in Figure 1-2, of the four bits not used for the converter magnitude, one is used to show the sign of the value, one is used to note overrange values, and the remaining two are not used and are set to zero.