several of them in parallel, while respecting the various timing
specifications of each DRAM bank and avoiding conflicts for the shared
data lines. Going further in this direction, a controller able to
-complete transfers out of order can provide more performance by:
-(1) grouping together requests by DRAM row, in order to minimize time
- spent on precharging and activating banks.
-(2) grouping together requests by direction (read or write) in order to
- minimize delays introduced by bus turnaround and write recovery
- times.
+complete transfers out of order can provide even more performance by:
+(1) grouping requests by DRAM row, in order to minimize time spent on
+ precharging and activating banks.
+(2) grouping requests by direction (read or write) in order to minimize
+ delays introduced by bus turnaround and write recovery times.
(3) being able to complete a request that hits a page earlier than a
concurrent one which requires the cycling of another bank.
- DATA_W must supply data to the controller from the appropriate
write transaction, on the cycle after they have been called using
CALL and TAG_CALL.
- - DATA_WM are the byte-granularity write data masks. They are used
- in combination with DATA_W to identify the bytes that should be
+ - DATA_WM are the byte-granular write data masks. They are used in
+ combination with DATA_W to identify the bytes that should be
modified in the memory. The DATA_WM bit should be high for its
corresponding DATA_W byte to be written.
ACK <0><0><1><0><0><0><1><0><1><1>
TAG ------<A>---------<B>---<C><D>
-SDRAM burst width and clock ratios
-==================================
+SDRAM burst length and clock ratios
+===================================
A system using ASMI must set the SDRAM burst length B, the ASMIbus word
width W and the ratio between the ASMIbus clock frequency Fa and the
SDRAM I/O frequency Fi so that all data transfers last for exactly one