The 4 C's |
Corey's home page |
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
[I've elided the listing of the demo board DIP switches. If you need
them, e-mail me.]
- 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.
- What voltage should be supplied to the Vref pin for proper
The Vref pin is for ADC reference voltage, so 20K to 30K is
- What is the recommended input audio voltage level for
The HM2006/2007 AGC (automatic gain control) specification is 0 dB
to 40dB. For example, an acceptable input level range is 20mV to
- 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.
- What is the required SRAM speed?
The SRAM access time should be less than 200ns.
- 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.]
- What is the response time after the read/write
The response time is about 5us.
- 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.
- 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
- What are device input/output levels?
They are TTL compatible.
- 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.
- Can the TEST pin be used for any purpose?
The TEST pin is for in house mass production testing only.
- Does the RDY have an internal current limiting resistor for
DC spec issue 3.35V Irdy=8mA (define with LED voltage drop 5V-3.35V
- What is the sequence of the demo board when it is powered
The intial sequence is 1) check SRAM, 2) initial SRAM, 3) light LED
with 00 and output RDY signal and 4) recognition mode.
- What do the socre numbers returned by the RESULT command
The score number is the different (distance) value between training
and recognition. The lower the value the more accurate.
- What is the command procedure with the null write
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.]
- 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
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.
Corin Anderson |
Last modified: Wed Aug 20 23:49:15 PDT 2003