ADAT is a protocol to transmit audio data over either coaxial or optical cables. The data transmission rate is determined by the transmitter, and the receiver has to recover the sample rate. ADAT normally carries 8 channels.
Important characteristics of ADAT software are the following:
Note that ADAT of eight channels at 48 Khz is identical to two channels at 192 KHz - a single bit in the data stream differentiates it (but the bit rates, transmit, and receive code are identical).
This module can transmit S/PDIF signals at the following rates (assuming eight threads on a 400 MHz part):
| Functionality provided | Resources required | Status | |||
| Channels | Sample Rate | 1-bit port | Threads | Memory | |
| 8 | up to 48 KHz | 1-2 | 1+ | 3.6K | Implemented and tested |
| 8 | up to 48 KHz | 1-2 | 1 | 3.5K | Implemented and tested |
It requires a single thread to run the transmit code. The number of 1-bit ports depends on whether the master clock is already available on a one-bit port. If available, then only a single 1-bit port is required to output ADAT. If not, then two ports are required, one for the signal output, and one for the master-clock input.
An external flip-flop is required to resynchronise the data signal to the master-clock if more than 2 channels are used, or if the sample rate is higher than 48 KHz.
The precise transmission frequencies supported depend on the availability of an external clock (eg, a PLL or a crystal oscillator) that runs at a frequency of:
512 * sampleRate
or a power-of-2 multiple. For example, for 48 Khz the external clock has to run at a frequency of 24.576 MHz. If both 44,1 and 48 Khz frequencies are to be supported, both a 24.587 MHz and a 22.579 MHz master clock are required. This is normally not an issue since the same clocks can be used to drive the audio codecs.
Typical applications for this module include iPod docks, digital microphones, digital mixing desks, USB audio, and AVB.
This module can receive ADAT signals at the following rates (assuming 8 threads on a 400 MHz part (?)):
| Functionality provided | Resources required | Status | ||
| Channels | Sample Rate | 1-bit port | Memory | |
| 8 | up to 48 KHz | 1 | 1.5-3.5 KB | Implemented and tested |
A single 50-MIPS thread is required. The receiver does not require any external clock, but can only recover 44.1 and 48 KHz sample rates. The amount of memory depends on whether both 44.1 and 48 KHz are to be supported, or just a single frequency.
Typical applications for this module include digital speakers, digital mixing desks, USB audio, and AVB.