Intel
®
81341 and 81342—DDR SDRAM Memory Controller
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
568
Order Number: 315037-002US
7.3.1.3
Memory Transaction Queues
There are two sets of transaction queues for transactions which address the DMCU DDR
Memory Space: transaction queue for north internal bus transactions and transaction
queue for south internal bus transactions. The dedicated units that are connected to
the DMCU do not support transaction queues.
7.3.1.3.1
North Internal Bus Port Transaction Queue (NIBPTQ)
The NIBPTQ stores memory transactions from the north internal bus. The NIBPTQ
supports 16 read transactions, each with up to 32 bytes buffer. The NIBPTQ also
supports 16 posted write transactions up to 32 Bytes each.
7.3.1.3.2
South Internal Bus Port Transaction Queue (SIBPTQ)
The SIBPTQ stores memory transactions from the south internal bus. The SIBPTQ
supports 8 read transactions, each with up to 1024 bytes buffer. The SIBPTQ also
supports 8 posted write transactions up to 1024 Bytes each.
7.3.1.4
Configuration Registers
The Configuration Registers block contains all of the memory-mapped registers listed in
Section 7.8, “Register Definitions” on page 625
. These registers define the memory
subsystem connected to the 81341 and 81342. The status registers indicate the
current DMCU status.
7.3.1.5
Refresh Counter
The Refresh Counter block keeps track of when the DDR SDRAM devices need to be
refreshed. The refresh interval is programmed in the
. Once the 12-bit refresh counter reaches the programmed interval, the
DDR SDRAM state machine issues a refresh command to the DDR SDRAM devices.
When a transaction is currently in progress, the DDR SDRAM State Machine waits for
the completion of the transaction to issue the refresh cycle. See
SDRAM Refresh Cycle” on page 606
for more details.
Note:
When the memory controller is completing transactions from the north internal bus
transaction queue (NIBPTQ) when the refresh counter expires, the DMARB completes
the NIBPTQ tenure based on the
“DMCU Port Transaction Count Register — DMPTCR” on
, before any refresh cycles are issued.
Note:
When the memory interface is busy when the refresh counter expires, it is possible for
the DMCU to generate more than one refresh cycle when the memory interface
becomes available.
7.3.1.6
Memory Controller Arbiter (DMARB)
The DMARB determines what transaction to issue next to the DDR SDRAM Control Unit.
The DMARB is configurable to adjust the selection of transactions from the DMCU ports
and the refresh counter. The DMARB selects transactions from all memory ports based
on a programmable arbitration scheme as described in
Arbitration and Configuration” on page 570
.