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AMC7823 default values

Frank
Intellectual 985 points

Other Parts Discussed in Thread: AMC7823, AMC7832, AMC7823EVM

Hello,

I'm using a AMC7823 Evaluation Module labled as:
AMC7823_REV A
BOM 6468330_REV D

According to the AMC7823 DATA SHEET (SLAS453E-APRIL 2005-REVISED JANUARY 2010, Revision E) from the following page:

http://www-s.ti.com/sc/ds/amc7823.pdf

the AMC7832 should deliver default values (see Table 2 on page 21 of 53).

When I'm reading Page 1 resgister after reset, I get the following values:

Addr  Value
0x00  0x0000
0x01  0x1000
0x02  0x2000
0x03  0x3000
0x04  0x4000
0x05  0x5000
0x06  0x6000
0x07  0x7000
0x08  0x0000
0x09  0x0000
0x0A  0x4000
0x0B  0x0000
0x0C  0x0000
0x0D  0x0000
0x0E  0x0FFF
0x0F  0x0000
0x10  0x0FFF
0x11  0x0000
0x12  0x0FFF
0x13  0x0000
0x14  0x0FFF
0x15  0x0000
0x16  0x0000
0x17  0x0000
0x18  0x0000
0x19  0x0000
0x1A  0x0000
0x1B  0x0000
0x1C  0x0000
0x1D  0x0000
0x1E  0x4000

The page 1 register at addr 0x1E should deliver 0xE000 (according Table 2) but I'm receiving 0x4000.

Q1: Do I have an older AMC revision or is there something wrong with the documentation?

The default values for DAC-[0..7] Data are all 0x0000 according Table 2, but I'm receiving also the DAC Addresses (see page 1 registers 0x00 to 0x07).
Q2: I believe reading also the DAC Addresses is OK and it is just not described in the documentation, correct?

Thanks,
Frank

  • 0
    TI__Guru**** 182731 points

    Hi Frank,

    For Q1, the AMC7823EVM may have an older revision of the silicon mounted to the board.  Can you tell us what the date code is?  This would be the series of numbers in the second two lines of text on the top surface of the chip mounted to the board.  We'll verify Q2 for you soon...

  • 0 in reply to Tom Hendrick
    Intellectual 985 points

    Hi Tom,

    the chip on the board is labled as follows:

    AMC7823
    TI 73W
    Z83D

    Just for the case I've an older chip, can you then provide the data sheet for it (if it is different to the latest one)?

    Thanks,
    Frank

  • 0 in reply to Frank
    TI__Guru**** 182731 points

    Hi Frank,

    The AMC7823 device you have on your evaluation board is from March of 2007.  The data sheet that was on the web at that time is attached.  In this document the device ID is described as 0x4000, but there is no mention of the DAC address coming along for the ride so we're still looking into that.

    slas453c.pdf
  • 0 in reply to Tom Hendrick
    TI__Expert 6925 points

    Hello Frank,

    Although Table 2 specifies DAC registers default value as 0x0000, when a DAC register is read, it returns the DAC channel in bits 14-12. These bits are named OCH (Output channel) found in Table 14 (page 42) of the old datasheet or in the table 15 (page 42) of the latest datasheet.

    OCH bits are read-only, so writing to them will not change them or affect the functionality of the register.

    We will update the datasheet in order to show this in Table 2.

    Regards,