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