National CP3BT26 User Manual
157
www.national.com
CP3
BT26
20.7.9
Audio Clock Control Register (ACCR)
The ACCR register is used to control the bit timing of the au-
dio interface. After reset, this register is clear.
dio interface. After reset, this register is clear.
CSS
The Clock Source Select bit selects one out of
two possible clock sources for the audio inter-
face. After reset, the CSS bit is clear.
0 – The Auxiliary Clock 1 is used to clock the
two possible clock sources for the audio inter-
face. After reset, the CSS bit is clear.
0 – The Auxiliary Clock 1 is used to clock the
Audio Interface.
1 – The 48-MHz USB clock is used to clock
the Audio Interface.
FCPRS
The Frame Clock Prescaler is used to divide
the bit clock to generate the frame clock for
the receive and transmit operations. The bit
clock is divided by (FCPRS + 1). After reset,
the FCPRS field is clear. The maximum al-
lowed bit clock rate to achieve an 8 kHz frame
clock is 1024 kHz. This value must be set cor-
rectly even if the frame sync is generated ex-
ternally.
the bit clock to generate the frame clock for
the receive and transmit operations. The bit
clock is divided by (FCPRS + 1). After reset,
the FCPRS field is clear. The maximum al-
lowed bit clock rate to achieve an 8 kHz frame
clock is 1024 kHz. This value must be set cor-
rectly even if the frame sync is generated ex-
ternally.
BCPRS
The Bit Clock Prescaler is used to divide the
audio interface clock (selected by the CSS bit)
to generate the bit clock for the receive and
transmit operations. The audio interface input
clock is divided by (BCPRS + 1). After reset,
the BCPRS[7:0] bits are clear.
audio interface clock (selected by the CSS bit)
to generate the bit clock for the receive and
transmit operations. The audio interface input
clock is divided by (BCPRS + 1). After reset,
the BCPRS[7:0] bits are clear.
20.7.10 Audio DMA Control Register (ADMACR)
The ADMACR register is used to control the DMA support
of the audio interface. In addition, it is used to configure the
automatic transmission of the audio control bits. After reset,
this register is clear.
of the audio interface. In addition, it is used to configure the
automatic transmission of the audio control bits. After reset,
this register is clear.
RMD
The Receive Master DMA field specify which
slots (audio channels) are supported by DMA,
i.e. when a DMA request is asserted to the
DMA controller. If the RMDn bit is set for an
assigned slot n (RXDSAn = 1), a DMA request
n is asserted, when the ARDRn is full. If the
RXDSAn bit for a slot is clear, the RMDn bit is
slots (audio channels) are supported by DMA,
i.e. when a DMA request is asserted to the
DMA controller. If the RMDn bit is set for an
assigned slot n (RXDSAn = 1), a DMA request
n is asserted, when the ARDRn is full. If the
RXDSAn bit for a slot is clear, the RMDn bit is
ignored. The following table shows the receive
DMA request scheme.
DMA request scheme.
TMD
The Transmit Master DMA field specifies
which slots (audio channels) are supported by
DMA, i.e. when a DMA request is asserted to
the DMA controller. If the TMD bit is set for an
assigned slot n (TXDSAn = 1), a DMA request
n is asserted, when the ATDRn register is
empty. If the TXDSA bit for a slot is clear, the
TMD bit is ignored. The following table shows
the transmit DMA request scheme.
which slots (audio channels) are supported by
DMA, i.e. when a DMA request is asserted to
the DMA controller. If the TMD bit is set for an
assigned slot n (TXDSAn = 1), a DMA request
n is asserted, when the ATDRn register is
empty. If the TXDSA bit for a slot is clear, the
TMD bit is ignored. The following table shows
the transmit DMA request scheme.
ACD
The Audio Control Data field is used to fill the
remaining bits of a 16-bit slot if only 13, 14, or
15 bits of PCM audio data are transmitted.
remaining bits of a 16-bit slot if only 13, 14, or
15 bits of PCM audio data are transmitted.
ACO
The Audio Control Output field controls the
number of control bits appended to the PCM
data word.
00 – No Audio Control bits are appended.
01 – Append ACD0.
10 – Append ACD1:0.
11 – Append ACD2:0.
number of control bits appended to the PCM
data word.
00 – No Audio Control bits are appended.
01 – Append ACD0.
10 – Append ACD1:0.
11 – Append ACD2:0.
7
1
0
FCPRS
CSS
15
8
BCPRS
7
4
3
0
TMD
RMD
15
13
12
11
10
8
Reserved
ACO
ACD
RMD
DMA Request Condition
0000
None
0001
ARDR0 full
0010
ARDR1 full
0011
ARDR0 full or ARDR1 full
x1xx
Not supported on
CP3BT26
1xxx
TMD
DMA Request Condition
0000
None
0001
ATDR0 empty
0010
ATDR1 empty
0011
ATDR0 empty or
ATDR1 empty
x1xx
Not supported on
CP3BT26
1xxx