
Digital Audio Interface (EBU)
MOTOROLA
Audio Functions
17-13
17.3.1
IEC958 RECEIVE INTERFACE
The IEC958 receive interface consists of 2 blocks:
1. The source selector
2. The IEC958 receiver itself
The source is selected by programming the appropriate EBU Control Register bits 7:6. The receiver then
extracts the data from the stream and outputs the data on the internal audio bus. The data can then be
used by the processor (using the PDIR and other registers) or by the IIS or EBU transmit interface. In the
case of the data being used as input to one of the IIS transmitters, the data rate of the incoming EBU data
must match exactly with that of the IIS transmitter. The following functions are performed by the block.
17.3.1.1
Audio Data Reception
The IEC958 receive block (19) extracts the audio data from the stream and puts this in 20-bit format on
Internal Audio Data bus. The format is exactly the same as the format produced by the serial data
interfaces.
17.3.1.2
Control Channel Reception
For a description of the control (or “C”) channel in EBU data formatting, refer to IEC958-3 description of
control channel. There are two 32-bit registers, one for each receiver, which receive the first 32 bits of the
“C” channel. No interpretation is done. See
Table 17-12Bits are ordered first bit left. So, C-channel bit “0” is seen in bit position 31 in the EBURcvCChannel
register. C-channel bit “31” is seen as the LSB bit in the register.
17.3.1.3
Control Channel Interrupt (IEC958 “C” Channel New Frame)
When the value of a new IEC958 “c” channel frame is loaded into the EBURcvCChannel register, an
interrupt is generated. This interrupt is cleared when the processor writes the corresponding bit in the
InterruptClear register. EBURcvCChannel is double buffered. Meaningful values can be read at any time.
17.3.1.4
Validity Flag Reception
An interrupt is associated with the Validity flag. (interrupt 24 - IEC958ValNoGood). This interrupt is set
every time a frame is seen on the IEC958 interface with the validity bit set to “invalid”.
Table 17-12 EBURcvCChannel Register
BITS
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
FIELD
EBURCVC CHANNEL1 AND CHANNEL2
RESET
----------------
R/W
READ ONLY
BITS
15
14
13
12
11
10
9876543210
FIELD
EBURCVC CHANNEL1 AND CHANNEL2
RESET
----------------
R/W
READ ONLY
ADDR
EBU1RCVCCHANNEL MBAR2 + 0X24:
EBU2RCVCCHANNEL MBAR2 + 0XD4:
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
..
.