EP4SE360F35I4 Datasheet, PDF (114/432 Pages) Altera Corporation – This section provides a complete overview of all features relating to the Stratix IV device family, which is the most architecturlly advanced

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Chapter 4: DSP Blocks in Stratix IV Devices
Stratix IV Operational Mode Descriptions
Use the rounding and saturation function just described in regular supported
multiplication operations, as specified in Table 4–2 on page 4–8. However, for
accumulation-type operations, use the following convention:
The functionality of the round logic unit is in the format of:
Result = RND[S(A × B)], when used for an accumulation type of operation.
Likewise, the functionality of the saturation logic unit is in the format of:
Result = SAT[S(A × B)], when used for an accumulation type of operation.
If you use both the rounding and saturation logic units for an accumulation type of
operation, the format is:
Result = SAT[RND[S(A × B)]]
DSP Block Control Signals
The Stratix IV DSP block is configured using a set of static and dynamic signals. You
can configure the DSP block dynamic signals. You can set the signals to toggle or not
toggle at run time. Table 4–9 lists the dynamic signals for the DSP block.
Table 4–9. DSP Block Dynamic Signals (Part 1 of 2)
Signal Name
■ signa
■ signb
output_round
chainout_round
output_saturate
chainout_saturate
Function
Signed/unsigned control for all multipliers and adders.
■ signa for “multiplicand” input bus to dataa[17:0] to each
multiplier
■ signb for “multiplier” input bus datab[17:0] to each multiplier
■ signa = 1, signb = 1 for signed-signed multiplication
■ signa = 1, signb = 0 for signed-unsigned multiplication
■ signa = 0, signb = 1 for unsigned-signed multiplication
■ signa = 0, signb = 0 for unsigned-unsigned multiplication
Round control for the first stage round and saturation block.
■ output_round = 1 for rounding on multiply output
■ output_round = 0 for normal multiply output
Round control for the second stage round and saturation block.
■ chainout_round = 1 for rounding multiply output
■ chainout_round = 0 for normal multiply output
Saturation control for the first stage round and saturation block for
Q-format multiply. If you enable both rounding and saturation,
saturation is done on the rounded result.
■ output_saturate = 1 for saturation support
■ output_saturate = 0 for no saturation support
Saturation control for the second stage round and saturation block for
Q-format multiply. If you enable both rounding and saturation,
saturation is done on the rounded result.
■ chainout_saturate = 1 for saturation support
■ chainout_saturate = 0 for no saturation support
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Stratix IV Device Handbook
Volume 1
February 2011 Altera Corporation