Altera DDR SDRAM High-Performance Controllers and ALTMEMP Bedienungsanleitung Seite 112

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Seitenansicht 111
6–18 Chapter 6: Functional Description—High-Performance Controller II
Sequence of Operations
External Memory Interface Handbook Volume 3 June 2011 Altera Corporation
Section I. DDR and DDR2 SDRAM Controllers with ALTMEMPHY IP User Guide
The AFI interface receives the write command from the arbiter and requests the
corresponding write data from the write data buffer.
The PHY receives the write command and the write data, through the AFI
interface.
Read Command
When a requesting master issues a read command, the following events occur:
The input interface accepts the read command.
The input interface passes the read command to the command generator.
The command generator processes the command and sends it to the timing bank
pool.
Once all timing requirements are met, the timing bank pool sends the command to
the arbiter.
When rank timing requirements are met, the arbiter grants the command request
from the timing bank pool and passes the read command to the AFI interface.
The AFI interface receives the read command from the arbiter and passes the
command to the PHY.
The PHY receives the read command through the AFI interface, and returns read
data through the AFI interface.
The AFI interface passes the read data from the PHY to the read data buffer.
The read data buffer sends the read data to the master through the input interface.
Read-Modify-Write Command
A read-modify-write command can occur when enabling ECC for partial write, and
for ECC correction commands. When a read-modify-write command is issued, the
following events occur:
The command generator issues a read command to the timing bank pool.
The timing bank pool and arbiter passes the read command to the PHY through
the AFI interface.
The PHY receives the read command, reads data from the memory device, and
returns the read data through the AFI interface.
The read data received from the PHY passes to the ECC block.
The read data is processed by the write data buffer.
When the write data buffer issues a read-modify-write data ready notification to
the command generator, the command generator issues a write command to the
timing bank pool; the arbiter then issues the write request to the PHY through the
AFI interface.
When the PHY receives the write request, it passes the data to the memory device.
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