cp3cn17 National Semiconductor Corporation, cp3cn17 Datasheet - Page 108

• Manufacturer Part Number: cp3cn17
• Description: Reprogrammable Connectivity Processor With Can Interface
• Manufacturer: National Semiconductor Corporation

www.national.com
of the first data bit or the first slot begins at the first positive
edge of the shift clock after the negative edge on the frame
sync pulse.
If the corresponding Frame Sync Select (FSS) bit in the Au-
dio Control and Status register is set, the receive and/or
transmit path generates or recognizes long frame sync puls-
es. For 8-bit data, the frame sync pulse generated will be 6
bit shift clock periods long, and for 16-bit data the frame
sync pulse can be configured to be 13, 14, 15, or 16 bit shift
clock periods long. When receiving frame sync, it should be
active on the first bit of data and stay active for a least two
bit clock periods. It must go low for at least one bit clock pe-
riod before starting a new frame. When long frame sync
pulses are used, the transfer of the first word (first slot) be-
gins at the first positive edge of the bit shift clock after the
positive edge of the frame sync pulse. Figure 49 shows ex-
amples of short and long frame sync pulses.
(SCK/SRCLK)
Bit Shift Clock
Figure 49. Short and Long Frame Sync Pulses
Short Frame
Long Frame
(STD/SRD)
Sync Pulse
Sync Pulse
Shift Data
D0
SCK
STD
SFS
D1
D2
D0
D3
D1
D4
Figure 50. Audio Slot with Audio Control Data
D2
D5
D3
D6
D4
13-bit PCM Data Word
D7
D5
16-bit Slot
DS156
D6
D7
108
D8
Some codecs require an inverted frame sync signal. This is
available by setting the Inverted Frame Sync bit in the
AGCR register.
16.6.3
The audio interface provides the option to fill a 16-bit slot
with up to three data bits if only 13, 14, or 15 PCM data bits
are transmitted. These additional bits are called audio con-
trol data and are appended to the PCM data stream. The
AAI can be configured to append either 1, 2, or 3 audio con-
trol bits to the PCM data stream. The number of audio data
bits to be used is specified by the 2-bit Audio Control On
(ADMACR. ACO[1:0]) field. If the ACO field is not equal to
0, the specified number of bits are taken from the Audio
Control Data field (ADMACR. ACD[2:0]) and appended to
the data stream during every transmit operation. The
ADC[0] bit is the first bit added to the transmit data stream
after the last PCM data bit. Typically, these bits are used for
gain control, if this feature is supported by the external PCM
codec.Figure 50 shows a 16-bit slot comprising a 13-bit
PCM data word plus three audio control bits.
D9
D10
Audio Control Data
D11
D12
ACD2
Control
Audio
ACD1
Bits
ACD0
DS161