Texas Instruments TMS320C64x DSP Benutzerhandbuch

3-37

The transport stream interface (TSI) capture mode captures MPEG-2 trans-
port data.

The video port TSI capture mode supports the following features:

-

Supports SYNC detect using the PACSTRT input from a front-end device.

-

Data capture at the rising edge of incoming VCLK1.

-

Parallel data reception.

-

Maximum data rate of 30 Mbytes/second.

-

Programmable packet size.

-

Hardware counter mechanism to timestamp incoming packet data.

-

Programmable filtering of packets with errors.

-

Interrupt to the DSP, based on absolute system time or system time clock
cycles.

The video port does not perform following functions; these functions should be
performed in software:

-

PID filtering

-

Data parsing

-

De-scrambling of data

Eight-bit parallel data is received on the input data bus. Data is captured on
the rising edge of VCLKIN. The data consists typically of 188-byte packets,
with the first byte a SYNC byte (also called a preamble). The capture packet
length is determined by the value of VCASTOP.

Data on the data bus is considered valid and captured only when the CAPEN
signal is active. TSI data capture begins with a SYNC byte as indicated by
PACSTRT (and CAPEN) active. (The SYNC byte may have any value.) Data
is captured on each VCLK rising edge when CAPEN is active until the entire
packet has been captured, irrespective of additional PACSTRT transitions.
The end-of-packet condition occurs when the 24-bit capture byte counter (as
reflected by the VCYPOS and VCXPOS bits of VCASTAT) equals the value in
the VCYSTOP and VCXSTOP bits of VCASTOP. The captured data includes
both SYNC byte and the data payload as shown in Figure 3–22.

After a packet is captured, the video port waits for the next active PACSTRT
to begin capture of another packet. Received packet data is packed into 64 bits
before being written to the FIFO.