www.ti.com
Appendix A
VDP Status
Address
C6h
Read only
7
6
5
4
3
2
1
0
FIFO full
FIFO
TTX
CC field 1
CC field 2
WSS/CGMS
VPS/Gemstar
VITC
error
empty
available
available
available
available
2x available
available
The VDP status register indicates whether data is available in either the FIFO or data registers, and status information about the FIFO.
Reading data from the corresponding register does not clear the status flags automatically. These flags are only reset by writing a 1 to the
respective bit. However, bit 6 is updated automatically.
FIFO full error:
0
No FIFO full error
1
FIFO was full during a write to FIFO.
The FIFO full error flag is set when the current line of VBI data can not enter the FIFO. For example, if the FIFO has only 10 bytes left and
teletext is the current VBI line, the FIFO full error flag is set, but no data is written because the entire teletext line will not fit. However, if the
next VBI line is closed caption requiring only 2 bytes of data plus the header, this goes into the FIFO. Even if the full error flag is set.
FIFO empty:
0
FIFO is not empty.
1
FIFO is empty.
TTX available:
0
Teletext data is not available.
1
Teletext data is available.
CC field 1 available:
0
Closed caption data from field 1 is not available.
1
Closed caption data from field 1 is available.
CC field 2 available:
0
Closed caption data from field 2 is not available.
1
Closed caption data from field 2 is available.
WSS/CGMS available:
0
WSS/CGMS data is not available.
1
WSS/CGMS data is available.
VPS/Gemstar 2x available:
0
VPS/Gemstar 2x data is not available.
1
VPS/Gemstar 2x data is available.
VITC available:
0
VITC data is not available.
1
VITC data is available.
VDP FIFO Word Count
Address
C7h
7
6
5
4
3
2
1
0
Number of words
This register provides the number of words in the FIFO. 1 word equals 2 bytes.
VDP FIFO Interrupt Threshold
Address
C8h
7
6
5
4
3
2
1
0
Number of words
This register is programmed to trigger an interrupt when the number of words in the FIFO exceeds this value (default 80h). This interrupt
must be enabled at address C1h. 1 word equals 2 bytes.
15
SLEA104 – July 2010
TVP5154A VBI Quick Start
Copyright © 2010, Texas Instruments Incorporated
