Altera Embedded Peripherals IP User Manual
Page 190
Table 20-3: Transaction Supported
Transaction
Code
Avalon-MM Transaction
Description
0x00
Write, non-incrementing
address.
Writes data to the given address until the total number of
bytes written to the same word address equals to the
value specified in the
size
field.
0x04
Write, incrementing address. Writes transaction data starting at the given address.
0x10
Read, non-incrementing
address.
Reads 32 bits of data from the given address until the
total number of bytes read from the same address equals
to the value specified in the
size
field.
0x14
Read, incrementing address. Reads the number of bytes specified in the
size
field
starting from the given address.
0x7f
No transaction.
No transaction is initiated. You can use this transaction
type for testing purposes. Although no transaction is
initiated on the Avalon-MM interface, the core still
returns a response packet for this transaction code.
The core can handle only a single transaction at a time. The
ready
signal on the core's Avalon-ST sink
interface is asserted only when the current transaction is completely processed.
No internal buffer is implemented on the data paths. Data received on the Avalon-ST interface is
forwarded directly to the Avalon-MM interface and vice-versa. Asserting the
waitrequest
signal on the
Avalon-MM interface backpressures the Avalon-ST sink interface. In the opposite direction, if the
Avalon-ST source interface is backpressured, the
read
signal on the Avalon-MM interface is not asserted
until the backpressure is alleviated. Backpressuring the Avalon-ST source in the middle of a read could
result in data loss. In such cases, the core returns the data that is successfully received.
A transaction is considered complete when the core receives an EOP. For write transactions, the actual
data size is expected to be the same as the value of the
size
field. Whether or not both values agree, the
core always uses the EOP to determine the end of data.
Malformed Packets
The following are examples of malformed packets:
• Consecutive start of packet (SOP)—An SOP marks the beginning of a transaction. If an SOP is
received in the middle of a transaction, the core drops the current transaction without returning a
response packet for the transaction, and initiates a new transaction. This effectively handles packets
without an end of packet(EOP).
• Unsupported transaction codes—The core treats unsupported transactions as a no transaction.
UG-01085
2014.24.07
Operation
20-3
Avalon Packets to Transactions Converter Core
Altera Corporation