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请教omap35中GPMC取数的建立保持时间



想请教各位专家,我是用omap35芯片。用GPMC方式异步读取数据,在OEOTIME有效后,信号的建立保持时间有多长?就是想问OE有效之后最长可以经过几个GPMC_FCLK把数据放到数据线上?

  • 你好,

    OEOFFSTIME减去OEONTIME就是你需要的时间。

    OEOFFSTIME和OEONTIME的长度可以在下面寄存器里面配置,理论上可以配置最大差值为31-0=31 GPMC_FCLK cycles。但是请注意,GPMC上的外部设备必须能够接受这样的时序才可以。

    The GPMC.GPMC_CONFIG4_i[3:0] OEONTIME field (where i = 0 to 7) defines the nOE/nRE signal
    assertion time relative to start access time. It is applicable only to read accesses.
    The GPMC.GPMC_CONFIG4_i[12:8] OEOFFTIME field defines the nOE/nRE signal deassertion time
    relative to start access time. It is applicable only to read accesses.

    12:8 OEOFFTIME nOE de-assertion time from start cycle time RW 0x10
    0x00: 0 GPMC_FCLK cycle
    0x01: 1 GPMC_FCLK cycle
    ...
    0x1F: 31 GPMC_FCLK cycles

    3:0 OEONTIME nOE assertion time from start cycle time RW 0x3
    0x0: 0 GPMC_FCLK cycle
    0x1: 1 GPMC_FCLK cycle
    ...
    0xF: 15 GPMC_FCLK cycles