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TM4C129XNCZAD: Accessing Flash Memory on the Micronix MX68GL1G0F using Dual Chip Select Mode with Address Latching

Nicholas Belanger
Prodigy 11 points
Part Number: TM4C129XNCZAD

I am currently attempting to interface with your MX68GL1G0F external flash device using a TI TM4C129XNCZAD microcontroller in dual select mode with address latching. I can confirm through test points that I am sending the appropriate signals for reading and writing operations to flash (CE# to low, RESET# to high, WE# or OE# to low depending on reading or writing and WP# to high). Despite this, when viewing the memory in a debugger or attempting to read from the memory all that I can see are 0xFF values for each byte, which should mean that we are in high impedance mode still for the flash chip. I have initialized the flash controller and set it's memory location in the TI microcontroller using TivaWare's peripheral library (specifically the External Peripheral Interface library). I can read and write to the other external peripheral being used in this setup using address latching. Does anyone know if there are additional steps that I need to do for accessing flash memory on microcontroller? 

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    TI__Guru**** 184366 points

    Hi 

    Nicholas Belanger said:
    I am currently attempting to interface with your MX68GL1G0F external flash device using a TI TM4C129XNCZAD microcontroller

    I want to first clarify that MX68GL1G0F is not a TI chip but TM4C129XNCZAD is. MX68GL1G0F is from Macronix and according to its product website, it is EOL. https://www.mxic.com.tw/en-us/products/NOR-Flash/Parallel-NOR-Flash/Pages/spec.aspx?p=MX68GL1G0F&m=Parallel%20NOR%20Flash&n=PM1727

    Nicholas Belanger said:
    I can confirm through test points that I am sending the appropriate signals for reading and writing operations to flash

    Here you are saying that the signals that come out of the MCU is correct. 

    Nicholas Belanger said:
    Despite this, when viewing the memory in a debugger or attempting to read from the memory all that I can see are 0xFF values for each byte, which should mean that we are in high impedance mode still for the flash chip.

    If you are sending the correct command to the flash for read or write operations and the flash is returning 0xFF then I will suggest you contact the flash vendor for support. Show them exactly the signal waveforms from a logic analyzer that were sent to the flash and the data is 0xFF. 

    Nicholas Belanger said:
    I can read and write to the other external peripheral being used in this setup using address latching.

    If you had experience with the EPI in the past to interface with other peripherals successfully then I tend to think your EPI initialization is correct. Perhaps it is something specific with the MX68GL1G0F that requires additional steps. However, I don't have experience with this 3rd party device and can't really know what exact steps are missing to read/write to it. If the vendor says the problem is is on the MCU's side on how the interface signals are generated then you can update this post again.