Augmented Dword 33 Bit Data Vectors

Many RT-XSG blocks communicating 32-bit data vectors (double words, or dwords) have input and/or output ports 33-bit wide.

This format is referred to as an Augmented Dword. The 33rd bit (the MSB) is a valid bit, used to sample the 32 LSBs by a register or a buffer.

Thus, the data output from the DataIN and from the ADC interface blocks can be sampled when the MSB is found to be active. In the same way, the DataOUT and the DAC interface blocks sample the input data when the MSB of the 33-bit inputs is active. A typical application of the 33rd bit of the Augmented Dword to register the data is illustrated by Figure 26.

In consequence, outputs from the first blocks can be fed directly to the inputs of the latter blocks, and the data sampling will be performed correctly.

Note: Even if the valid (33rd) bit is activated only once for each sample period of each signal of the DataIN and ADC interface blocks, the output data remains unchanged until the next valid data is available, indicated by a new pulse on the 33rd bit of each output vector.

Use of the 33rd bit of the Augmented Dword to register the 32-bit data vector