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Altera_Forum's avatar
Altera_Forum
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11 years ago

Max5 Power Monitor

Hello,

I'm working with the Arria starter kit. To start with, I've already seen this:

http://www.alterawiki.com/wiki/how_to_read_power_monitor_value_in_system_console

but I still have some questions.

1)How do I figure out what the reference voltage is for a given rail?

2)How do I figure out what the resistance is?

3)Where do these numbers comes from? sld_access_ir $vj 1 2 vs. sld_access_ir $vj 2 2

4)The output I get from sld_access_dr $vj 16 1

[list 0x00 0x00] looks like : 0x11 0x0, 0x16 0x0, etc..

is this backwards? I ask because the upper bytes shift wildly between 0x10 and 0x20, and the lower bytes are always 0x0, which seems backwards to me.

Thanks,

Jonah

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    11 years ago

    Hi Jonah,

    Yes, very likely it is "backwards" (i.e., the least significant byte is printed first).

    I am sort of reverse engineering Power Monitor's behavior to automate some measurements on a Cyclone IV Development Kit.

    Here are some observations, which may or not be true:

    - The values read seem to the the least significant bits of a 24-bit ADC; in the formulas, some have advised dividing the reference voltage by 23 and multiplying by the value read.

    - You can read the resistance values by looking at the components on the PCB, or by looking and the schematics or datasheets for your board.

    - I believe all rails use the same reference voltage, because it is a single configuration for the whole ADC. In my board, it seems to be 5.37 or 5.0V.

    - The number changing from 1 to 2 in your question# 3 is the value to be written in the instruction register. The second value should be a timeout in microseconds.

    Hope this helps.

    Ricardo