Q
I've looed at the AD74111 AUDIO CODEC, and I didn't understand few things:1) What is the digital output level (TTL, RS232 or something else)
2) How can you program the AD74111?
3) Is there an evaluation board or a demo board?
4) Are there similar products to the AD74111 that have an evaluation board?
A
1. Digital input and output levels are given on page 3 of the datasheet. Thelogic high levels are expressed with respect to DVDD1. Since DVDD1 can be
anywhere from 2.375V to 3.6V, the CODEC can interface to processors with 3.3V
input/output as well processors with 2.5V I/O.
2. Firstly to clarify things, the AD74111 only contains volatile memory, there
is no non-volatile memory on board so the CODEC needs to be
programmed/initialised by the system processor each time the system power is
turned on.
The seven internal registers are controlled via the Serial port of the device.
By far the easiest way to program the device is using a DSP SPORT with the
CODEC in MASTER mode.
That means that the CODEC generates the Serial clock and therefore controls the
timing of the programming operation. Typically, you would use a DSP SPORT - you
would stack up a series of programming instructions into the transmit buffer
and then the CODEC would clock them out of the DSP - without any direct
synchronisation needed to the DSP code execution.
Figures 13 and 14 show the expected data format in MIXED mode - the first
16bits on the DIN line represent a control word. The control word format is
shown in Table V on page 15. there is a read write bit, a four-bit address
field (to access one of the seven on chip registers) and a 10-bit data field.
The first 16 bits on the DOUT line contain the contents of any registers that
the previous instruction requested to read back. If the previous operation was
a write then you can ignore the forst 16 bits on DOUT.
Once you are finished with programming the device, you can set the interface to
DATA mode or you can remain in MIXED mode. Once in DATA mode no further reading
or writing to the control registers is possible until the device is powered
down or reset.
3. There is an evaluation board for the part (see attached document). However,
the evaluation board does NOT allow programming of the device directly from a
PC interface. Instead the SPORT connector interfaces to the development systems
of our DSP products and we supply some example code for our ADSP-218x family of
DSPs. So you need a DSP development system (not necessarily from ADI) in order
to use the CODEC evaluation board and program the device.
4. We have a number of Audio Codecs. Many are intended for specialist
applications (PC sound cards using AC97 protocol, AV-receivers, etc) and are
not as suitable for other applications.