Visible to Intel only — GUID: iga1405375575865
Ixiasoft
Visible to Intel only — GUID: iga1405375575865
Ixiasoft
33.2.4.2. Sharing Data and Address Pins
When the controller shares pins with other tri-state devices, average access time usually increases and bandwidth decreases. When access to the tri-state bridge is granted to other devices, the SDRAM incurs overhead to open and close rows. Furthermore, the SDRAM controller has to wait several clock cycles before it is granted access again.
To maximize bandwidth, the SDRAM controller automatically maintains control of the tri-state bridge as long as back-to-back read or write transactions continue within the same row and bank.
This behavior may degrade the average access time for other devices sharing the Avalon® -MM tri-state bridge.
The SDRAM controller closes an open row whenever there is a break in back-to-back transactions, or whenever a refresh transaction is required. As a result:
- The controller cannot permanently block access to other devices sharing the tri-state bridge.
- The controller is guaranteed not to violate the SDRAM’s row open time limit.