saa7803 NXP Semiconductors, saa7803 Datasheet - Page 34

• Manufacturer Part Number: saa7803
• Description: Saa7803 One Chip Cd Audio Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13695
Objective data sheet
6.6.6.3 CD-TEXT interface
Table 9:
After finishing subcode read the microprocessor must release the interface to allow the
decoder to capture new subcode information. This is done by issuing a read to register
SubcodeQReadend.
The availability of a new subcode frame will also trigger an interrupt if bit
InterruptEnable2(SUBCODEREADYENABLE) is set.
The channel decoder contains an internal buffer which stores CD-TEXT information
(format 4, available in the lead-in area). The buffer can hold one CD-TEXT pack for
readback, while it receives at the same time the next pack.
The operation of the CD-TEXT readback interface is controlled via register
CDTEXTControl. Bit FREEZEEN determines whether or not the internal buffer is frozen
during readback (such that the next pack can not overwrite the current one before the
microprocessor has finished reading). Bit CRCFAILEN determines whether or not packs
with a failing CRC check are made available for readback.
This subcode can be retrieved by the microprocessor, by accessing the registers
CDTEXTStatus, CDTEXTData and CDTEXTReadEnd.
To start retrieving the CD-TEXT pack, the microprocessor must read the register
CDTEXTStatus first. This register contains various status bits that indicate the status of
the CD-TEXT pack that may be read. When, after reading the register CDTEXTStatus, the
TEXTREADY bit is found ‘1’, the CD-TEXT interface will be blocked (indicated by
TEXTBUSY going to ‘1’) to prevent new subcodes overwriting the current one; at least if
CDTEXTControl(FREEZEEN) is turned on. Bit TEXTCRCOK indicates if the current
CD-TEXT pack had correct data content by a hardware CRC check.
After reading CDTEXTStatus with TEXTREADY = '1', the microprocessor may retrieve as
many CD-TEXT bytes as required (maximum 16) by issuing subsequent reads to register
CDTEXTData.
After finishing CD-TEXT read the microprocessor must release the interface to allow the
decoder to capture new CD-TEXT information. This is done by issuing a read to register
CDTEXTReadEnd.
Address/Byte
1
2
3
4
5
6
7
8
9
10
Subcode Q-channel frame content
Name
CONTROL/MODE
TNO
POINT
REL MIN
REL SEC
REL FRAME
ZERO
ABS MIN
ABS SEC
ABS FRAME
Rev. 01 — 19 April 2005
Description
Mod100
Mod 60
Mod 75
0 or incremented modulo 10
Mod100
Mod 60
Mod 75
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
One chip CD audio device
Remark
relative time
absolute time
SAA7803
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