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I want to use SCIA and External memory interface both in an application using DSP TMS320F28335.

Sejal Gandhi
Intellectual 960 points

Other Parts Discussed in Thread: TMS320F28335

Hi Champs,

I have query regarding TMS320F28335. If I want to use SCIA and External memory interface both in an application, I found that, address pin XA-19 and XR/W is conflict with SCITXDA (SCIA) pin. So what is alternate?

Can I use only 16 lines of address bus (XA0 - XA15)? and then can PIN XA-19 be used for SCITXDA?

If I use zone0 for external interface, is it require to connect all address bus (20 bits)? Can I use only 16 lines of address bus (XA0 - XA15) because zone 0 uses external addresses 0X00000 to 0x00FFF?

Waiting for reply.

Regards,

Sejal

  • 0
    TI__Guru* 93800 points

    Sejal Gandhi said:
    If I use zone0 for external interface, is it require to connect all address bus (20 bits)? Can I use only 16 lines of address bus (XA0 - XA15) because zone 0 uses external addresses 0X00000 to 0x00FFF?

    Yes - if the memory is not large enough to need the address line then yes it can be used for something else.  This is true on the other zones as well.

    Please note that zone 0 has what is called "write followed by read" protection which can slow down back to back accesses.  For pure memory this is not needed but is instead more suitable for peripherals connected to the bus.  This is documented in section 1.4 of the XINTF guide. www.ti.com/lit/SPRU949

    -Lori

  • 0 in reply to Lori Heustess
    TI__Intellectual 960 points

    Thanks Lori,

    So, Zone 0, 6 & 7 all  can be used with only 16 adderss lines (XA0 : 15). Can I select any Data bus width?

    Each XINTF zone can individually be configured for a 16-bit or 32-bit wide data bus.

    If I am using 16 bit address bus, can I configure any data bus width or only I have to select 16-bit data bus?

    Regards,

    Sejal

     

  • 0 in reply to Sejal Gandhi
    TI__Guru* 93800 points

    Sejal Gandhi said:

    So, Zone 0, 6 & 7 all  can be used with only 16 adderss lines (XA0 : 15). Can I select any Data bus width?

    Each XINTF zone can individually be configured for a 16-bit or 32-bit wide data bus.

    Correct.

    Sejal Gandhi said:
    If I am using 16 bit address bus, can I configure any data bus width or only I have to select 16-bit data bus?

    You can select either x16 or x32 bus.  Just remember the physical connection for A0/WE change depending on your configuration.

    -Lori