Bt860/861
3.0 Digital Processing and Functionality
3.2 Effects
Multiport YCrCb to NTSC/PAL /SECAM
CRC data is not calculated and must be provided by the user. Figure 3-19
illustrates a typical CGMS signal. Note that bit 1 is closest to the HSYNC pulse
and bit 20 is farthest. The amplitude of the CGMS pulses are 70 IRE when high,
and 0 IRE when low. For further CGMS details, see specifications
EIA-J CPR-1202, EIA-J CPR-1204, and IEC 61880.
Figure 3-19. CGMS Waveform
V
IRE
100
1.0
Bit No.
1
Reference
2
3
.. .. .. 20
0.786
70
0.286
0
0
2.235 µs ± 50 ns
–40
11.2 µs ± 0.3 µs
49.1 µs ± 0.44 µs
Line 20/283
861_003
3.2.18 Closed Captioning and Extended Data Services
The Bt860/861 can produce Closed Captioning (CC) and Extended Data Services
(XDS) waveforms for NTSC and PAL on the lines specified by CC_SEL (49[3:0])
and XDS_SEL (49[7:4]), as listed in Table 3-12. Two bytes of CC data are entered
using registers CCB1 (42[7:0]) and CCB2(43[7:0]), and two bytes of XDS data are
entered using registers XDSB1 (40[7:0]) and XDSB2 (41[7:0]). The data registers
are double buffered to prevent accidental overwriting of the data. To enable CC, set
register bit ECC (48[0]) high, and to enable XDS, set register bit EXDS (48[1])
high. To prevent writing partial data sequences, data is not latched until the second
byte of the two-byte data sequence (CCB2 or XDSB2) is written. Therefore, data
must be written in the order Byte 1, then Byte 2.
Table 3-12. Closed Captioning and Extended Data Services Control Bits
0x49
D7
D6
D5
D4
D3
D2
D1
D0
XDS_SEL
CC_SEL
525 Line
625 Line
285
336
284
335
283
334
282
333
22
24
21
23
20
22
19
21
D860DSA
Conexant
3-29
CONEXANT [ CONEXANT SYSTEMS, INC ]
