Altera RapidIO MegaCore Function - Manual (Page 170)

7–8 Chapter 7: Testbenches
RapidIO MegaCore Function August 2014 Altera Corporation
User Guide
NREAD Transactions
The next set of transactions tested are NREADs. The DUT sends a group of NREAD
transactions to the sister_rio module by cycling the read burst size from 8 to
MAX_READ_BYTES
in increments of 8 bytes. For each iteration, the rw_addr_data task is
called. This task is defined in the bfm_io_read_master instance of the Avalon-MM
master BFM. The task performs the read request packets across the I/O Avalon-MM
Slave Read interface. The read transaction across the Avalon-MM interface is
translated into a RapidIO NREAD request packets. The values of the rd_address,
rd_byteenable
, and rd_burstcount parameters determine the values for the rdsize,
wdptr and xamsbs fields in the header of the RapidIO packet.
The NREAD request packets are received by the DUT and are translated into
Avalon-MM read transactions that are presented across the sister_rio module‘s I/O
master Avalon-MM interface. An instance of avalon_bfm_slave, the BFM for an
Avalon-MM slave, is driven by this interface. The read operations are checked and
data is returned by calling the task, write_readdata. This task drives the data and
read
datavalid control signals on the Avalon-MM master read port of the DUT.
The returned data is expected at the DUT’s I/O Avalon-MM slave interface. The
rw_data
task is called and it captures the read data. This task is defined inside the
instance of bfm_io_read_master. The read data and the expected value are then
compared to ensure that they are equal.
Doorbell Transactions
To test DOORBELL messages, the doorbell interrupts must be enabled. To enable
interrupts, the testbench sets the lower three bits in the Doorbell Interrupt Enable
register located at address 0x0000_0020. The test also programs the DUT to store all of
the successful and unsuccessful DOORBELL messages in the Tx Completion FIFO.
For more information, refer to Table 6–65 on page 6–29 .
Next, the test pushes eight DOORBELL messages to the transmit DOORBELL Message FIFO
of the DUT. The test increments the message payload for each transaction, which
occurs when the rw_addr_data task (defined in the bfm_drbell_s_master instance) is
invoked with a ‘WRITE operation to the TX doorbell register at offset 0x0000_000C.
This action programs the 16-bit message, an incrementing payload in this example, as
well as the DESTINATION_ID—0x55 for an 8-bit device ID or 0x5555 for a 16-bit device
ID—which is used in the DOORBELL transaction packet.
To verify that the DOORBELL request packets have been sent, the test waits for the
drbell_s_irq
signal to be asserted. The test then reads the Tx Doorbell Completion
register (refer to Table 6–63 on page 6–28 ). This register provides the DOORBELL
messages that have been added to the Tx Completion FIFO. Eight successfully
completed DOORBELL messages should appear in that FIFO and each one should be
accessible by reading the Tx Doorbell Completion register eight times in succession.
To perform this verification, the test invokes the rw_data task defined in the instance
bfm_drbell_s_master.
If you created the DUT with Doorbell Rx enable turned on and with Doorbell Tx
enable turned off, the doorbell test programs the sister_rio module to send eight
DOORBELL
messages to the DUT. The test verifies that all eight DOORBELL messages were
received by the DUT. The test calls the rw_addr_data task defined in the instance
sister_bfm_drbell_s_master. The task performs a write to the Tx Doorbell register