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发表于 2015-04-11 22:38:22
请教一个CPU与FPGA接口时序约束的问题,下图是CPU测接口时序:
现在的约束如下:
1. 对地址锁存信号,分别对信号上升沿和下降沿设置input delay
set_input_delay -rise -max -clock [get_clocks {CLK}] t11max [get_ports {ALE}]
set_input_delay -rise -min -clock [get_clocks {CLK}] t11min [get_ports {ALE}]
set_input_delay -add_delay -fall -max -clock [get_clocks {CLK}] t21max [get_ports {ALE}]
set_input_delay -add_delay -fall -min -clock [get_clocks {CLK}] t21min [get_ports {ALE}]
2. 对片选信号:
set_input_delay -rise -max -clock [get_clocks {CLK}] t24max [get_ports {CPU_CS1 CPU_CS2}]
set_input_delay -rise -min -clock [get_clocks {CLK}] t24min [get_ports {CPU_CS1 CPU_CS2}]
set_input_delay -add_delay -fall -max -clock [get_clocks {CLK}] t14max [get_ports {CPU_CS1 CPU_CS2}]
set_input_delay -add_delay -fall -min -clock [get_clocks {CLK}] t14min [get_ports {CPU_CS1 CPU_CS2}]
3. 对读信号和写信号约束:
set_input_delay -rise -max -clock [get_clocks {CLK}] t20x [get_ports {CPU_WRH CPU_WRL}]
set_input_delay -rise -min -clock [get_clocks {CLK}] t20n [get_ports {CPU_WRH CPU_WRL}]
set_input_delay -add_delay -fall -max -clock [get_clocks {CLK}] t10max [get_ports {CPU_WRH CPU_WRL}]
set_input_delay -add_delay -fall -min -clock [get_clocks {CLK}] t10min [get_ports {CPU_WRH CPU_WRL}]
4. FPGA-TO-CPU的数据输出
set_output_delay -clock {get_clocks {CLK}} -max t30 [get_ports {CPU_D}] -add_delay
set_output_delay -clock {get_clocks {CLK}} -min t31 [get_ports {CPU_D}] -add_delay
以上约束不知正确与否?
剩下还需要约束CPU-TO-FPGA的数据输入,不知该如何处理?
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