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If Allow backpressure is turned on, the waitrequest signal is asserted whenever the data_in master tries
to write to a full FIFO buffer. waitrequest is only deasserted when there is enough space in the FIFO
buffer for a new transaction to complete. waitrequest is asserted for read operations when there is no
data to be read from the FIFO buffer, and is deasserted when the FIFO buffer has data.
Figure 16-1: FIFO with Avalon-MM Input and Output Interfaces
S
Avalon-MM Slave Po rt
On-Chip FIFO
Memory
S S
SS
Wr
Rd
Input Status I/F
(optiona l)
Output Statu s I/F
(optiona l)
sys tem interconne ct fabric
Input dat a
Output data
Avalon-ST Sink to Avalon-ST Source
This configuration has streaming input and output interfaces as illustrated in the figure below. You can
parameterize most aspects of the Avalon-ST interfaces including the bits per symbol, symbols per beat,
and the width of error and channel signals. The input and output interfaces must be the same width. If
Allow backpressure is turned on, both interfaces use the ready and valid signals to indicate when space
is available in the FIFO core and when valid data is available.
For more information about the Avalon-ST interface protocol, refer to the Avalon Interface Specifica‐
tions.
Figure 16-2: FIFO with Avalon-ST Input and Output Interfaces
SNK
Avalon-ST Sink
On-Chip FIFO
Memory
S S
SNK
SRC
Input Status I/F
(optiona l)
Output Statu s I/F
(optiona l)
System Interconn ect Fab ric
Streaming
Output Dat a
SRC
Avalon-ST Sou rce
S
Avalon-MM Slave Port
Avalon-MM Write Slave to Avalon-ST Source
In this configuration, the input is an Avalon-MM write slave with a width of 32 bits as shown in the FIFO
with Avalon-MM Input Interface and Avalon-ST Output Interface figure below. The Avalon-ST output
(source) data width must also be 32 bits. You can configure output interface parameters, including: bits
16-2
Avalon-ST Sink to Avalon-ST Source
UG-01085
2014.24.07
Altera Corporation
On-Chip FIFO Memory Core
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