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2–8 Chapter 2: Qsys Tutorial

Verifying Avalon-ST DUT

Avalon Verification IP Suite User Guide May 2011 Altera Corporation

As Example 2–1 illustrates, when the Avalon-ST source BFM drives a transaction, it

also prints the transaction to the ModelSim transcript window, creating a record of the

test. The Avalon-ST Sink BFM also prints the transactions it receives on the transcript

window. The Avalon-ST Sink BFM compares the transaction it receives with the one

sent by the Avalon-ST Source BFM, and the results of the comparison are printed on

the transcript window.

In Example 2–1 the idles values for the source and sink are different. The Avalon-ST

Source BFM sets the number of idle cycles to zero using the

set_transaction_idles

function. The Avalon-ST Sink BFM waits for three cycles before receiving the first

transaction because it takes three cycles for the transaction to propagate from the

input port to the output port of the Avalon-ST Single-Clock FIFO buffer. The

difference in values for the idle field is not an error because the Avalon-ST interface

protocol allows source and sink components to have different latencies.

The extract of the simulation results in the ModelSim transcript console shown in

Example 2–2 displays the source response latency, which is the number of clock cycles

the Avalon-ST Single-Clock FIFO buffer takes when the Avalon-ST Single-Clock FIFO

buffer backpressures the Avalon-ST Source BFM. The third response shows a non-zero

response latency. During the third transaction, the Avalon-ST Single-Clock FIFO

buffer is full so it is not able to receive the transaction. As a result, the Avalon-ST

Single-Clock FIFO buffer backpressures the Avalon-ST Source BFM.

# 1130000: INFO: top.pgm.print_transaction: EOP: 0

# 1130000: INFO: top.pgm.print_transaction: Channel: 0

# 1130000: INFO: top.pgm.print_transaction: Error: 0

# 1130000: INFO: top.pgm.print_transaction: Empty: 0

# 1130000: INFO: top.pgm.compare_transaction: Transaction 1 compare OK

# 1150000: INFO: top.pgm.print_transaction: Sink BFM: Receive transaction 2

# 1150000: INFO: top.pgm.print_transaction: Data: 2

# 1150000: INFO: top.pgm.print_transaction: Idles: 0

# 1150000: INFO: top.pgm.print_transaction: SOP: 0

# 1150000: INFO: top.pgm.print_transaction: EOP: 0

# 1150000: INFO: top.pgm.print_transaction: Channel: 0

# 1150000: INFO: top.pgm.print_transaction: Error: 0

# 1150000: INFO: top.pgm.print_transaction: Empty: 0

# 1150000: INFO: top.pgm.compare_transaction: Transaction 2 compare OK

# 1190000: INFO: top.pgm.print_transaction: Sink BFM: Receive transaction 3

# 1190000: INFO: top.pgm.print_transaction: Data: 3

# 1190000: INFO: top.pgm.print_transaction: Idles: 0

# 1190000: INFO: top.pgm.print_transaction: SOP: 0

# 1190000: INFO: top.pgm.print_transaction: EOP: 1

# 1190000: INFO: top.pgm.print_transaction: Channel: 0

# 1190000: INFO: top.pgm.print_transaction: Error: 0

# 1190000: INFO: top.pgm.print_transaction: Empty: 0

# 1190000: INFO: top.pgm.compare_transaction: Transaction 3 compare OK

# 1190000: INFO: top.pgm: Test Passed

Example 2–2. Response Latency

# 1030000: INFO: top.pgm.test_threads.source_response_thread: Source response latency 0

# 1050000: INFO: top.pgm.test_threads.source_response_thread: Source response latency 0

# 1090000: INFO: top.pgm.test_threads.source_response_thread: Source response latency 1

# 1110000: INFO: top.pgm.test_threads.source_response_thread: Source response latency 0

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