Overview - Stanford Research Systems DS360 Operating Manual And Programming Reference

Overview

The DS360 is capable of generating digital domain waveforms in two different digital audio formats. The
two formats are AES-EBU, the professional digital audio format and S/PDIF, the consumer digital audio
format.
The following description is provided to help user understand the operation of the DS360's digital output.
It by no means completely describes any of the specifications. For complete information, the user should
obtain copies of the relevant standards (AES-EBU 1992, IEC 958, ANSI S4.40-1992 and EIAJ CP-340).
Digital Audio Data Encoding
The two formats of digital audio communication are very similar in terms of data format
and encoding. Both formats support data rate of 32 kHz, 44.1 kHz and 48 kHz. Each
audio sample is transmitted in a sub-frame. Each sub-frame consists of a preamble, 4 bits
of auxiliary data, 20 bits of audio data and one bit each of validity, user, channel and
parity. Two sub frames are combined to make a frame, 192 of which make up a block.
The channel bits of each sub-frame are combined to make up 24 eight bit bytes that
convey status information. The first four bytes contain most of the important status
information. The significance of the first four bytes of channel status bits of each
interface are indicated below.
byte bit 0
0 Pro=1
1
2 AUX Use
3
byte bit 0
0 Pro=0
1
2
3 Sampling Frequency
AES-EBU
The AES-EBU digital audio interface format is described in AES3-1992 (also ANSI
S4.40-1992). It is a means of serially transmitting two channels of periodically sampled
audio signals on a single shielded twisted wire pair. The transmission rate is such that
both audio channels can be transmitted in one sample period. Error detection is provided
and there is a format for transmitting channel status (control) and user specific
information. The control and user specific data is transmitted at the rate of one bit per
sample.
Professional Mode Channel Status Bytes
bit 1 bit 2
Audio Emphasis
Channel Mode
Consumer Mode Channel Status Bytes
bit 1 bit 2
Audio Copy
Category Code
Source Number
bit 3 bit 4
User Management
Word Length
Reserved
bit 3 bit 4
Emphasis
Channel Number
Clock Accuracy
DS360 Ultra Low Distortion Function Generator
Digital Output
bit 5 bit 6
Lock Sampling Frequency
Reserved
bit 5 bit 6
Mode
Gen Stat
Reserved
5-3
bit 7
bit 7