Altera FIR Compiler Manual de usuario descargar pdf (Pagina 61)

Chapter 4: Functional Description 4–19

Timing Diagrams

This filter accepts an input every clock cycle and produces an output every clock

cycle. Because ast_source_ready and ast_sink_valid are kept at high, the

filter can internally run fully streaming. An input is transferred when

ast_sink_ready and ast_sink_valid are both high during the rising edge of the

clock.

Figure 4–16 shows a three channel filter with the same specification as the single

channel filter in Figure 4–15.

The FIR filter now has start of packet (sop) and end of packet (eop) signals for both

the sink (input) and source (output) modules. The first input data to the FIR filter is

accompanied by the high value of the ast_sink_sop port, which means it belongs

to the first channel.

The third input data is marked as an end of packet by the high value of the

ast_sink_eop port. This sequence repeats itself continuously at each cycle.

When the filter output is ready, ast_source_valid goes high, and for the first data

output ast_source_sop goes high to mark the start of the packet. The

ast_source_channel output shows to which channel that particular output

belongs. The last channel data is marked with the high value of the

ast_source_eop port.

Figure 4–17 and Figure 4–18 on page 4–20 demonstrate another single channel, single

rate filter timing diagram. In these diagrams, the FIR filter requires input data every

three clock cycles and produces one output data every three clock cycles. In general,

MCV multicycle filters (when the Clocks to Compute value is greater than one),

Multibit Serial filters, and Serial filters require a new input data every N clock cycles

where N represents the following:

■ For an MCV multicycle filter, N is the clocks to compute value

■ For a Multibit Serial filter, N = (input data bit width)/(number of serial units)

■ For a Serial filter, N = (input data bit width +1)

Figure 4–16. Three Channel, Single Rate (Parallel or MCV Single Cycle)

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Altera FIR Compiler Manual de usuario Pagina 61