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OMAP-L138: Trigger for data transfer through EMIFA

Aobo Guan
Prodigy 110 points
Part Number: OMAP-L138


Hello,

We are using the EMIFA interface of DSP core to communicate asynchronous device. I have a question on controlling the EMIFA data transfer:

Is it possible that we copy a 50 byte array to the memory location SOC_EMIFA_CS5_ADDR to SOC_EMIFA_CS5_ADDR + 50, instead of putting them on the data and address line immediately, we could set a trigger to start the transition. In other words, while we are copying the array byte by byte, the DSP doesn't send any data out until we issue the start command.

Regards,

Albert

  • 0
    TI__Guru**** 161600 points
    Hi Albert,

    It should be possible to put the data into internal memory (i.e. shared RAM) and output it on the EMIFA data pins when you issue a command.

    I am not sure what you mean by memory locatin SOC_EMIFA_CS5_ADDR + 50. The CSx pins are connected to the external memories... see section 20.2.3 Pin Descriptions in OMAP-L138 Technical Reference Manual.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    Prodigy 110 points
    Hi Yordan,

    Thanks for replying to my question!

    It seems that as soon as I copy any information to the EMIFA memory segment, the DSP puts data on the bus. I'm wondering is there a way to hold the EMIFA data transfer, and using a trigger to start the transition.

    Regards,
    Albert
  • 0 in reply to Aobo Guan
    TI__Guru**** 161600 points
    Hi Albert,

    The data gets propagated to the data pins, as soon as you put it in the EMIFA buffers.
    See 20.2.5 Asynchronous Controller and Interface there are two modes of operation:
    Normal Mode:
    "The first mode of operation is Normal Mode, in which the EMA_WE_DQM pins of the EMIFA function as byte enables. In this mode, the EMA_CS[5:2] pins behaves as typical chip select signals, remaining active for the duration of the asynchronous access. See Section 20.2.5.1 for an example interface with multiple 8-bit devices."
    Select Strobe Mode:
    "in which the EMA_CS[5:2] pins act as a strobe, active only during the strobe period of an access. In this mode, the EMA_WE_DQM pins of the EMIFA function as standard byte enables for reads and writes. A summary of the differences between the two modes of operation are shown in Table 20-14. Refer to Section 20.2.5.4 for the details of asynchronous operations in Normal Mode, and to Section 20.2.5.5 for the details of asynchronous operations in Select Strobe Mode. The EMIFA hardware defaults to Normal Mode, but can be manually switched to Select Strobe Mode by setting the SS bit in the asynchronous m (m = 1, 2, 3, or 4) configuration register (CEnCFG) (n = 2, 3, 4, or 5). Throughout the chapter, m can hold the values 1, 2, 3 or 4; and n can hold the values 2, 3, 4, or 5"
    Extended Wait Mode:
    "The EMIFA also provides configurable cycle timing parameters and an Extended Wait Mode that allows the connected device to extend the strobe period of an access cycle. The following sections describe the features related to interfacing with external asynchronous devices."

    I think Select Strobe Mode & Extended Wait Mode are close to what you need.

    Best Regards,
    Yordan