SM5902AF Datasheet, PDF (31/40 Pages) Nippon Precision Circuits Inc – compression and non compression type shock-proof memory controller

SM5902AF
Digital audio interface
When the DIT flag is set to 1, the digital audio inter- data structure is modulated using a preamble and
face output from pin DIT is enabled. The output biphase mark encoding.
M Channel 1 W Channel 2 B Channel 1 W Channel 2 M Channel 1 W Channel 2
Sub Frame
Sub Frame
Frame 191
Frame 0
Frame 1
Start Block
Figure 5. Frame format
0
34
78
Preamble
(Sync Groupe)
Auxiliary
Digital Audio Sample Data
27 28
31
VUC P
Audio Sample Validity
User Bit Data
Audio Channel Status
Sub Frame Parity
Figure 6. Subframe format
Preamble
The preamble is a particular bit pattern used to per-
form subframe and block synchronization and dis-
crimination, assigned to one of 4 time slot divisions
(0 to 3), comprising 8 continuous biphase modulat-
ed transfer rate status indicators.
There are 3 types of preamble. The leading pream-
ble pattern of all blocks is preamble pattern B,
which is then followed by preamble pattern M for
channel 1, and preamble pattern W for channel 2.
Preamble
Channel coding
Leading symbol = 0
Leading symbol = 1
B
11101000
00010111
M
11100010
00011101
W
11100100
00011011
The SM5902AF starts with 0, so only the preamble patterns for leading symbol = 0 are used.
Digital audio sample data and auxiliary audio
The digital audio sample data is a 20-bit digitized
audio signal. Auxiliary audio data, on the other
hand, can be audio sample data of varying length.
The SM5902AF uses a 16-bit audio data structure
internally with audio data output bits 4 to 11 set to 0
and bits 12 to 27 output in LSB first format.
Audio sample validity
The validity flag is set to 0 when the digital audio
sample data is output correctly, or it is set to 1 if the
output is incorrect. It is also set to 1 if encoding
does not start when the device is operating in
forced mute, microcontroller forced mute, and
shockproof mode.
NIPPON PRECISION CIRCUITS-31