我的板子是am3517,设置gpmc功能,异步16位数据线,设置wrofftime=1f(31个fclk周期),cstime=1f,片选周期和写周期都是31个fclk周期,且波形都很正常,我是单步通信,每隔一秒钟写一个数据,示波器显示数据的保持时间只有片选的一半,根据datasheet上看异步不复用写模式数据应该保持到写周期结束,如图所示,黄线是片选信号,蓝线是数据表示1,但是后来又降低为0了,请ti的工程师帮忙分析一下,最近被这个事情搞的吃不好睡不好的。
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我的板子是am3517,设置gpmc功能,异步16位数据线,设置wrofftime=1f(31个fclk周期),cstime=1f,片选周期和写周期都是31个fclk周期,且波形都很正常,我是单步通信,每隔一秒钟写一个数据,示波器显示数据的保持时间只有片选的一半,根据datasheet上看异步不复用写模式数据应该保持到写周期结束,如图所示,黄线是片选信号,蓝线是数据表示1,但是后来又降低为0了,请ti的工程师帮忙分析一下,最近被这个事情搞的吃不好睡不好的。
datasheet里面有这一节,这个怎么理解啊?
9.1.5.3.10 Bus Keeping Support
At the end-cycle time of a read access, if no other access is pending, the GPMC drives the bus with the
last data read after RDCYCLETIME completion time to prevent bus floating and reduce power
consumption.
After a write access, if no other access is pending, the GPMC keeps driving the data bus after
WRCYCLETIME completes with the same data to prevent bus floating and power consumption.
谢谢你的回复。
我模拟的是norflash,外设其实是继电器低速设备,我调用gpmc.c里面的函数,引脚默认配置都是gpmc功能,我在board-am3517ev.c这个文件里写入