SAA2501 Datasheet, PDF (29/52 Pages) NXP Semiconductors – Digital Audio Broadcast DAB decoder

Philips Semiconductors
Digital Audio Broadcast (DAB) decoder
Preliminary specification
SAA2501
7.20.8 INPUT DATA FRAME HEADER ITEMS
Information about the input data, derived by the SAA2501
from the input data frame headers, may be read from the
frame header items. Both the frame header bytes decoded
from the input bitstream and the header bytes used for the
actual decoding may be read.
The decoded frame header item is valid independent of the
value of status flag INSYNC, it e.g. shows the decoded
headers while the SAA2501 is in the process of
synchronizing.
The used frame header item is only valid if status flag
INSYNC is set. The used header bytes are derived by the
SAA2501 from the decoded header bytes by overruling
NOPR to 0 if settings bit CRCACT = 1, and overruling
detected errors.
Table 24 Decoded input data frame header item; 3 bytes (read-only)
SUBSEQUENT
BYTES
Decoded header
byte 1
Decoded header
byte 2
Decoded header
byte 3
7
SY3⁽¹⁾
BR3⁽⁶⁾
MOD1⁽⁸⁾
6
SY2⁽¹⁾
5
SY1⁽¹⁾
4
SY0⁽¹⁾
3
ID⁽²⁾
2
LAY1⁽³⁾
1
LAY0⁽⁴⁾
0
NOPR⁽⁵⁾
BR2⁽⁶⁾
BR1⁽⁶⁾
BR0⁽⁶⁾
FS1⁽⁷⁾
FS0⁽⁷⁾ undefined undefined
MOD0⁽⁸⁾ MODX1⁽⁹⁾ MODX0⁽⁹⁾ COPR⁽¹⁰⁾ ORIG⁽¹¹⁾ EMPH1⁽¹²⁾ EMPH0⁽¹²⁾
Table 25 Used input data frame header item; 3 bytes (read-only)
SUBSEQUENT
BYTES
Used header
byte 1
Used header
byte 2
Used header
byte 3
7
6
5
4
3
2
1
0
1
1
1
1
1
1
LAY0⁽⁴⁾ NOPR⁽⁵⁾
BR3⁽⁶⁾
BR2⁽⁶⁾
BR1⁽⁶⁾
BR0⁽⁶⁾
FS1⁽⁷⁾
FS0⁽⁷⁾ undefined undefined
MOD1⁽⁸⁾ MOD0⁽⁸⁾ MODX1⁽⁹⁾ MODX0⁽⁹⁾ COPR⁽¹⁰⁾ ORIG⁽¹¹⁾ EMPH1⁽¹²⁾ EMPH0⁽¹²⁾
Notes to “Table 24” and “Table 25”
1. SY3 to SY0; last 4 bits of the synchronization word. For ISO/MPEG only; undefined for EU147 input data.
2. ID; algorithm identification. For ISO/MPEG only; undefined for EU147 input data.
3. LAY1; layer Most Significant Bit (MSB). For ISO/MPEG only; undefined for EU147 input data.
4. LAY0; layer Least Significant Bit (LSB). When decoding EU147 input data these bits are undefined in the decoded
header byte and equal 0 in the used header byte.
5. NOPR; CRC on header, bit allocation and scale factor select information activity flag. When decoding EU147 input
data these bits are undefined in the decoded header byte and equal 0 in the used header byte.
6. BR3 to BR0; bit rate index.
7. FS1 and FS0; sample rate index.
8. MOD1 and MOD0; mode.
9. MODX1 and MODX0; mode extension.
10. COPR; copyright flag.
11. ORIG; original or home copy flag.
12. EMPH1 and EMPH0; audio de-emphasis, these bits are only meant to monitor the current de-emphasis mode; the
corresponding de-emphasis is performed by the SAA2501 automatically before the baseband audio signal is output.
January 1995
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