doc: cosmetic changes

This commit is contained in:
Sebastien Bourdeauducq 2012-01-27 14:35:58 +01:00
parent bf2f6f31e3
commit 5466a82933
1 changed files with 9 additions and 10 deletions

View File

@ -28,12 +28,11 @@ should be able to peek ahead at the incoming requests and service
several of them in parallel, while respecting the various timing several of them in parallel, while respecting the various timing
specifications of each DRAM bank and avoiding conflicts for the shared specifications of each DRAM bank and avoiding conflicts for the shared
data lines. Going further in this direction, a controller able to data lines. Going further in this direction, a controller able to
complete transfers out of order can provide more performance by: complete transfers out of order can provide even more performance by:
(1) grouping together requests by DRAM row, in order to minimize time (1) grouping requests by DRAM row, in order to minimize time spent on
spent on precharging and activating banks. precharging and activating banks.
(2) grouping together requests by direction (read or write) in order to (2) grouping requests by direction (read or write) in order to minimize
minimize delays introduced by bus turnaround and write recovery delays introduced by bus turnaround and write recovery times.
times.
(3) being able to complete a request that hits a page earlier than a (3) being able to complete a request that hits a page earlier than a
concurrent one which requires the cycling of another bank. concurrent one which requires the cycling of another bank.
@ -81,8 +80,8 @@ The data signals are used to complete requests.
- DATA_W must supply data to the controller from the appropriate - DATA_W must supply data to the controller from the appropriate
write transaction, on the cycle after they have been called using write transaction, on the cycle after they have been called using
CALL and TAG_CALL. CALL and TAG_CALL.
- DATA_WM are the byte-granularity write data masks. They are used - DATA_WM are the byte-granular write data masks. They are used in
in combination with DATA_W to identify the bytes that should be combination with DATA_W to identify the bytes that should be
modified in the memory. The DATA_WM bit should be high for its modified in the memory. The DATA_WM bit should be high for its
corresponding DATA_W byte to be written. corresponding DATA_W byte to be written.
@ -112,8 +111,8 @@ STB <0><1><0><0><1><1><0><1><1><0>
ACK <0><0><1><0><0><0><1><0><1><1> ACK <0><0><1><0><0><0><1><0><1><1>
TAG ------<A>---------<B>---<C><D> 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 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 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 SDRAM I/O frequency Fi so that all data transfers last for exactly one