OMAPL-138 and VTPIO_CTRL register

Adam Turowski

Other Parts Discussed in Thread: AM1808, OMAPL138

Hi all,

I am using AISgen to convert executable generated by CodeSourcery_G++_Lite tools package into format which is understand by OMAPL-138 bootloader. AISgen front end allows to set up a lot of DDR controller register, but I don't find anything that sets VTPIO_CTL register. My code doesn't touch any of DDR registers. In SPRUGJ4B on page 64 there is a description of bits D0, D1 and D2 in VTPIO_CTL register, which are responsible for OMAP drive strength.

The questions are:

1) Who is setting VTPIO_CTL register and who is performing DDR IO buffer calibration described in chapter 2.13.1 in SPRUGJ4B document? Bootloader?

2) Who is setting bits D0, D1 and D2 in VTPIO_CTL? What the values of these bits mean?

Best regards,

Adam

over 13 years ago

0 Mukul Bhatnagar over 13 years ago

TI__Guru* 83985 points

Hi Adam

The following post is on AM1808, but is applicable to OMAPL138 too

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/p/135592/500421.aspx#500421

The boot loader will typically take care of the calibration. it can be performed as part of the initialization software too (you will see the steps in the OMAPL138 GEL File).

You might find the following wiki useful too

http://processors.wiki.ti.com/index.php/DDR_Interface_Drive_Strength

Regards

Mukul

0 Adam Turowski over 13 years ago in reply to Mukul Bhatnagar

Prodigy 190 points

Hi Mukul,

Thanks for the information. According to the forum post you are referring to, the bootloader performs impedance calibration. After that there is another thing that needs to be set: actual OMAPL-138 drive strength. Reading between lines page 64 in SPRUGJ4B and bottom of http://processors.wiki.ti.com/index.php/DDR_Interface_Drive_Strength I presume that this is controlled by bits D0-D2 in VTPIO_CTL register. So I am still missing the answer to my second question: who is settting those bits and what is the meaning of these bits values in terms of actual OMAPL-138 drive strength?

Best regards,

Adam

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OMAPL-138 and VTPIO_CTRL register