Siemens S50037 ユーザーズマニュアル
SieMo S50037 Data Book
PRELIMINARILY
16/30
Interface Description
PCM Interface
Overview
PCM Pulse Code Modulation is a
standard method used to digitise
human voice
human voice
Four-wire, full duplex serial interface
used to transfer a single voice channel
to an external audio codec
to an external audio codec
Maximum of one SCO connection is
possible using the PCM interface
Further SCO channels must use the
HCI protocol layer
Data format is 13 bit linear PCM
Description
Pulse Code Modulation (PCM) is the
standard method used to digitise human
voice patterns for transmission over digital
communication channels. Through its
PCM interface, SieMo provides hardware
support for continual transmission and
reception of PCM data, thus reducing
processor overhead for wireless headset
applications.
SieMo offers a bi-directional digital audio
interface that routes directly into the
baseband layer of the on-chip firmware (it
does not pass through the HCI protocol-
layer). Hardware on SieMo allows the data
to be sent to and received from a SCO
connection. Only one SCO connection can
be supported by the PCM interface at any
one time. Any additional SCO connections
must receive and transmit their data over
the HCI protocol layer. The data format is
13-bit linear PCM. SieMo can operate
either as a master (with an output clock of
256kHz) or as a slave (with the input clock
varying between 128kHz and 512kHz).
When in slave mode and using higher
clock rates SieMo can support Motorola's
Synchronous Serial Interface (SSI)
standard that allows multiple bi-directional
audio channels to be multiplexed onto a
single physical connection.
standard method used to digitise human
voice patterns for transmission over digital
communication channels. Through its
PCM interface, SieMo provides hardware
support for continual transmission and
reception of PCM data, thus reducing
processor overhead for wireless headset
applications.
SieMo offers a bi-directional digital audio
interface that routes directly into the
baseband layer of the on-chip firmware (it
does not pass through the HCI protocol-
layer). Hardware on SieMo allows the data
to be sent to and received from a SCO
connection. Only one SCO connection can
be supported by the PCM interface at any
one time. Any additional SCO connections
must receive and transmit their data over
the HCI protocol layer. The data format is
13-bit linear PCM. SieMo can operate
either as a master (with an output clock of
256kHz) or as a slave (with the input clock
varying between 128kHz and 512kHz).
When in slave mode and using higher
clock rates SieMo can support Motorola's
Synchronous Serial Interface (SSI)
standard that allows multiple bi-directional
audio channels to be multiplexed onto a
single physical connection.
Generic PCM Interface
For a generic PCM interface there is one
master and one slave device. The master
generates the clock and synchronisation
signals. The sync signal identifies the start
of the sample data and has an 8kHz
period. There are two types of frame sync:
long and short. In long frame sync mode
PCM_SYNC going high indicates the first
(and most significant) bit of the sample. It
must remain high for at least two clock
cycles, but this can be longer. In short
frame sync MSB start is signalled by sync
going low (normally it only goes high for
one clock cycle).
The clock runs at a higher rate than sync:
at least 8 x bits_per_sample MHz,
although higher rates are common. The
sample resolution is 13 bits/sample,
uncompressed. Several Motorola
CODECs allow their output gain to be
controlled via the addition of three extra
data bits after the audio data. SieMo
supports this feature, effectively raising the
bits per sample to 16. Data from both the
master and slave is clocked out on the
rising clock edge and sampled on the
falling edge. Master mode is the default
setting. In master mode SieMo generates
a 256kHz clock signal (PCM_CLK) and the
8kHz, long format synchronisation signal
(PCM_SYNC). Short frame sync is not
supported. See PCM Timing Diagrams for
more information.
Slave mode is selected by setting a
Persistent Store value. In slave mode
SieMo clocks output data on the rising
edge of the received clock signal and
samples incoming data on the falling edge.
The incoming clock frequency should be
between 128kHz and 512kHz. (Note that
128kHz is 8 x 16 kHz, therefore the
absolute minimum possible frequency for
the 8ksamples/sec and 16bits/sample (13
audio data plus three gain data). The
frame sync must be long format. Short
format is not supported (see SSI Mode
and Timing Diagrams in this section for
more information).
master and one slave device. The master
generates the clock and synchronisation
signals. The sync signal identifies the start
of the sample data and has an 8kHz
period. There are two types of frame sync:
long and short. In long frame sync mode
PCM_SYNC going high indicates the first
(and most significant) bit of the sample. It
must remain high for at least two clock
cycles, but this can be longer. In short
frame sync MSB start is signalled by sync
going low (normally it only goes high for
one clock cycle).
The clock runs at a higher rate than sync:
at least 8 x bits_per_sample MHz,
although higher rates are common. The
sample resolution is 13 bits/sample,
uncompressed. Several Motorola
CODECs allow their output gain to be
controlled via the addition of three extra
data bits after the audio data. SieMo
supports this feature, effectively raising the
bits per sample to 16. Data from both the
master and slave is clocked out on the
rising clock edge and sampled on the
falling edge. Master mode is the default
setting. In master mode SieMo generates
a 256kHz clock signal (PCM_CLK) and the
8kHz, long format synchronisation signal
(PCM_SYNC). Short frame sync is not
supported. See PCM Timing Diagrams for
more information.
Slave mode is selected by setting a
Persistent Store value. In slave mode
SieMo clocks output data on the rising
edge of the received clock signal and
samples incoming data on the falling edge.
The incoming clock frequency should be
between 128kHz and 512kHz. (Note that
128kHz is 8 x 16 kHz, therefore the
absolute minimum possible frequency for
the 8ksamples/sec and 16bits/sample (13
audio data plus three gain data). The
frame sync must be long format. Short
format is not supported (see SSI Mode
and Timing Diagrams in this section for
more information).