SAA2501 Datasheet, PDF (15/52 Pages) NXP Semiconductors – Digital Audio Broadcast DAB decoder

Philips Semiconductors
Digital Audio Broadcast (DAB) decoder
Preliminary specification
SAA2501
Table 7 Signals of coded data master input interface
SIGNAL
CDM
CDMEF
CDMCL
CDMWS
DIRECTION
input
input
output
output
FUNCTION
ISO/MPEG coded input data (master input)
coded data (master input) error flag
coded data (master input) bit clock
coded data (master input) word select
handbook, full pagewidth
CDM
CDMCL
CDMWS
CDMEF
1
2
16
17
n
1
2
valid data
1 unreliable data bit (example)
valid but unreliable data
invalid data
MGB495
Fig.7 Input data serial transfer format (master input).
Data clock CDMCL is being output, having a fixed
frequency of 768 kHz. Signal CDM carries the coded data
in bursts of 16 valid bits. Coded data input frames may
only start either at the first or at the ninth bit of a 16 bit valid
data burst (i.e. only at a byte boundary). The value of word
select signal CDMWS is changed every time new input
data is needed: one CDMCL period after each transition in
CDMWS, 16 bits of valid data are read serially. Assume N
is the number of CDMCL periods between two transitions
of CDMWS, and R is the number of CDMCL periods to
obtain the effective bit rate E (in kbits/s) at a transferring
data rate of 768 kbits/s, i.e. R = ^{1----6-----×}-E----7---6---8-- . The SAA2501
keeps N close to R, but N can vary plus or minus two:
N ∈ {round(R)−2,...,round(R)+2}.
Error flag CDMEF is used to indicate input data
insecurities (e.g. due to erratic channel behaviour). In
Fig.7, an example with one unreliable bit is shown. The
value of CDMEF may vary for each valid data bit, but is
combined by the SAA2501 for every group of 8 input bits.
7.17.2 THE CODED DATA SLAVE INPUT INTERFACE
The coded data slave input interface signals are shown in
Fig.8. The coded data master input interface consists of
5 signals (see Table 8).
January 1995
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