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Basic Elements 45
Xilinx Blocks
• Binary Point: Output binary point location
Other parameters used by this block are explained in the Common Parameters section
of the previous chapter.
The Parallel to Serial block does not use a Xilinx LogiCORE.
An error is reported when the number of output bits cannot be divided evenly by the
number of input bits. The minimum latency for this block is zero.
Set Valid Bit
The Xilinx Set Valid Bit block flags input data as invalid when the signal
on the valid bit input port is zero. This block only sets data invalid; it
cannot change input data to valid.
In the Xilinx Blockset, every data sample that flows through the model
is accompanied by a handshake validation signal. In the corresponding
hardware, every data-carrying bus has a companion net that carries a valid or invalid
status indicator. This block provides some explicit control over this handshake
mechanism.
Block Parameters Dialog Box
The block parameters dialog box can be invoked by double-clicking the icon in your
Simulink model.
Figure 3-20: Set Valid Bit block parameters dialog box
Slice
The Xilinx Slice block allows you to slice off a sequence of bits from your
input data and create a new data value. This value is presented as the
output from the block. The output data type is unsigned with its binary
point at zero.
The block provides several mechanisms by which the sequence of bits
can be specified. If the input type is known at the time of parameterization, the
various mechanisms do not offer any gain in functionality. If, however, a Slice block is
used in a design where the input data width or binary point position are subject to
change, the variety of mechanisms becomes useful. The block can be configured, for
example, always to extract only the top bit of the input, or only the integral bits, or