TMS320AV7110 datasheet(68/131 Pages) TI

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DSP

TMS320AV7110

Revision 3.1

10/08/99 22:18

Page 68

The MPEG2Lynx assumes the convention that MPEG-2 packets (M-packets) always have the highest

priority in using the Bulky Data interface. That is, the MPEG2Lynx will preempt an on-going

transmission of an I-packets before its completion to transmit an M-packet if it is ready for

transmission. An M-packet transmission, on the other hand, is never preempted.

Figure 23 shows the functionality of the interface signals when the ‘AV7110 reads data from the

MPEG2Lynx. The maximum input rate of MPEG-2 data coming from the MPEG2Lynx and routed

through the transport stream hardware demultiplexer block (TPP) is approximately 64.8 Mbits/second.

The maximum input bit rate over one transport packet is 60 Mbits/second. Additional timing details

can be found in Section 17.5.

byte p (pack. start byte) byte p+1

byte p+187 (last byte in fifo)

BDICLK

BDIF[2:0]

BDIRW

BDIEN

BDI[7:0]

BDAVAIL

(driven by LYNX)

(driven By LYNX)

byte p+n

Figure 23. 1394 Interface Read Sequence

13.1.2 The ‘AV7110 writes data to the MPEG2Lynx

When the ‘AV7110 writes data to the MPEG2Lynx (record mode), it drives BDIF, BDIEN, and

BDIRW for one clock (system) period. BDIEN is driven low for only one byte and must be driven high

between two byte transmissions. This is illustrated in Figure 24. Additional timing details can be found

in Section 17.5.

byte p (pack. start byte) byte p+1

byte p+187 (last byte in fifo)

BDICLK

BDIF[2:0]

BDIRW

BDIEN

BDI[7:0]

byte p+n

Figure 24. 1394 Interface Write Sequence

13.1.3 The ‘AV7110 Internal Data Path for 1394

In recording mode, the ‘AV7110 sends either encrypted or clean packets to the 1394 interface. The

packet is transferred as soon as it arrives. When recording encrypted data, the ECD module is

bypassed. In the case of recording decrypted data, the TPP sends the encrypted part of the payload to

the ECD module, and then forwards each byte to the 1394 interface. No CPU processing is done to the

packet during recording. The TPP automatically modifies the header if the packet is decrypted.

Note that the same bit stream cannot be sent to the 1394 interface twice (e.g., once after decryption, and

twice as part of a full transport stream with the by-pass capability). Both the MPEG2Lynx and the

‘AV7110 support only one MPEG-2 transport stream channel on the Bulky Data interface.

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