Datasheet

06 February 2012 Broadcom Europe Ltd. 406 Science Park Milton Road Cambridge CB4 0WW Page 119
© 2012 Broadcom Corporation. All rights reserved
8 PCM / I2S Audio
The PCM audio interface is an APB peripheral providing input and output of telephony or
high quality serial audio streams. It supports many classic PCM formats including I2S.
The PCM audio interface has 4 interface signals;
PCM_CLK - bit clock.
PCM_FS - frame sync signal.
PCM_DIN - serial data input.
PCM_DOUT - serial data output.
PCM is a serial format with a single bit data_in and single bit data_out. Data is always
serialised MS-bit first.
The frame sync signal (PCM_FS) is used to delimit the serial data into individual frames. The
length of the frame and the size and position of the frame sync are fully programmable.
Frames can contain 1 or 2 audio/data channels in each direction. Each channel can be
between 8 and 32 bits wide and can be positioned anywhere within the frame as long as the
two channels don’t overlap. The channel format is separately programmable for transmit and
receive directions.
PCM_CLK
PCM_FS
MS LSCh. 1 MS LSCh. 2PCM_DIN
PCM_DOUT
CH1POS
CH1WID
CH2WID
CH2POS
FSLEN
FLEN
MS LSCh. 1 MS LSCh. 2
CH1POS
CH1WID
CH2WID
CH2POS
Figure 8-1 PCM Audio Interface Typical Timing
The PCM_CLK can be asynchronous to the bus APB clock and can be logically inverted if
required.
The direction of the PCM_CLK and PCM_FS signals can be individually selected, allowing
the interface to act as a master or slave device.
The input interface is also capable of supporting up to 2 PDM microphones, as an alternative
to the classic PCM input format, in conjunction with a PCM output.