SAA7385 Datasheet, PDF (31/64 Pages) NXP Semiconductors – Error correction and host interface IC for CD-ROM SEQUOIA

Philips Semiconductors
Error correction and host interface IC for
CD-ROM (SEQUOIA)
Preliminary specification
SAA7385
10 FRONT-END
This Chapter explains the information of the front-end circuitry.
10.1 Minute Second Frame (MSF) addressing and header information
Table 40 Header mode and MSF from block decoder: 0xF092, F093, F09A and F09B
DATA BYTE
MNEMONIC R/W
7
6
5
4
3
2
1
0
MODE
R
MODE7 to MODE0
MINS
R
MINUTES7 to MINUTES0
SECS
R
SECONDS7 to SECONDS0
FRMS
R
FRAME7 to FRAME0
These registers contain the mode, minute, second and frame information from the header when in data mode. This data
is valid whenever the HDDRDY bit in the RDDSTAT register is set. In audio mode, the MSF address is taken from the
Q-channel information.
Table 41 Q-channel information: 0xF0A9, F0AA, F0AB, F0B1 and F0B2
DATA BYTE
MNEMONIC R/W
7
6
5
4
3
2
1
0
RDTK
R
TRACK7 to TRACK0
RDMD
R
MODE7 to MODE0
RDMN
R
ABSMIN7 to ABSMIN0
RDSC
R
ABSSEC7 to ABSSEC0
RDFM
R
ABSFRM7 to ABSFRM0
These registers contain the information taken from the raw sub-channel information from the CD decoder. Due to the fact
that this data has not had any error correction applied to it, it is necessary to perform a CRC check for validity. Twelve
bytes of Q-channel information are assembled from each sector of data; the last two bytes contain the CRC parity.
Therefore the validity of the contents of these registers can only be determined after the last bit has been loaded and
checked.
Table 42 Times from QCHRDY to BADQ (RDDSTAT)
SPEED
n=1
n=2
n=4
n=6
n=8
TIME (µs)
2 177
1 089
545
363
273
For example, at the n = 4 data rate, the BADQ flag
(in RDDSTAT) should be checked 545 µs after the
QFRMRDY interrupt (from RDDSTAT) is asserted.
If BADQ is LOW then the contents of the Q-channel
registers are valid; otherwise the CRC check failed and the
Q-channel information may be incorrect. If the data clock
is running (ECMD LOW or ENABRED HIGH) then BADQ
will be valid until the end of the sector; otherwise BADQ is
valid until the end of the next Q frame.
1996 Jun 19
31