The 4 C's | Corey's home page | Corey's Talking Toaster | FAQ | HM2007 FAQ from Images

Note: this is a copy of the FAQ that Images Company provided me for the HM2007. It represents their collection of notes for use with the HM2007 part. See my annotated datasheet for my take on how to use it.

Common questions asked about the HM2006/2007
and the demo board

  1. Does S1 have a purpose during the write cycle?
    S1 has no use in the write cycle so there is no difference with 1/0.
  2. What voltage should be supplied to the Vref pin for proper operation?
    The Vref pin is for ADC reference voltage, so 20K to 30K is acceptable.
  3. What is the recommended input audio voltage level for optimum performance?
    The HM2006/2007 AGC (automatic gain control) specification is 0 dB to 40dB. For example, an acceptable input level range is 20mV to 0.2V.
  4. Can any one of the crystal connection pins (X1, X2) be used as clock inputs or outputs?
    X1 can be used for input and X2 can be used for output.
  5. What is the required SRAM speed?
    The SRAM access time should be less than 200ns.
  6. Are K1-K4 in a high impedance state in all cases expect for a read cycle?
    In the write cycle, K1-K4 are inputs and in all other cases they are outputs. [Corin's note: this is very important! The HM2007 is usually driving the K-bus, so take care to not drive it from the microcontroller, too. I bridged the two chips with 10K resistors for an added measure of safety.]
  7. What is the response time after the read/write command?
    The response time is about 5us.
  8. Would loading "null data" accomplish a CLEAR function and what form would null data take?
    You can get the format from the upload command and null equals zero.
  9. What are typical word pattern lengths that are uploaded and are they fixed or variable length?
    The pattern length is fixed at 0.92 of a second or 1.92 seconds per word.
  10. What are device input/output levels?
    They are TTL compatible.
  11. What is the purpose of the AGND pin?
    The purpose of the AGND pin is to support 1/2 VDD. It can also connect 0.1uF to ground.
  12. Can the TEST pin be used for any purpose?
    The TEST pin is for in house mass production testing only.
  13. Does the RDY have an internal current limiting resistor for an LED?
    DC spec issue 3.35V Irdy=8mA (define with LED voltage drop 5V-3.35V = 1.65V).
  14. What is the sequence of the demo board when it is powered on?
    The intial sequence is 1) check SRAM, 2) initial SRAM, 3) light LED with 00 and output RDY signal and 4) recognition mode.
  15. What do the socre numbers returned by the RESULT command mean?
    The score number is the different (distance) value between training and recognition. The lower the value the more accurate.
  16. What is the command procedure with the null write cycle?
    This is only a defined protocol and has no meaning sometimes. [Corin's note: I don't fully understand this point, but if it refers to the null states in the flow charts, I found them unnecessary. See my annotated datasheet and assembly code for details.]
  17. Our prototype using 2007 has a tendency to power up in a random state, often from the CPU's perspective, in a "dead state" where it will not accept any commands. Is there a procedure to bring the device out of a "dead state."
    First, check if the power pin (two pins) are connected or not. Then check the rise rate of the power pin. The faster the better.
[I've elided the listing of the demo board DIP switches. If you need them, e-mail me.]
Corin Anderson |
Last modified: Wed Aug 20 23:49:15 PDT 2003