
VV5404 & VV6404
CD5404-6404F-A
13/54
The even parity bits are based on the following relationships:
1. An even number of ones in the 4-bit sequence (C
2
, C
1
, C
0
and P
0
).
2. An even number of ones in the 3-bit sequence (C
2
, C
1
, P
1
).
3. An even number of ones in the 3-bit sequence (C
2
, C
0
, P
2
).
4. An even number of ones in the 3-bit sequence (C
1
, C
0
, P
3
).
Table 6 shows how the parity bits maybe used to detect and correct 1-bit errors and detect 2-bit errors.
4.2.3
The last 2 bytes of the embedded control sequence contains supplementary data. This normally contains the current
line number except if the line code is the end of line, the 2 bytes are padded out using null characters (FF
H
). The 12
bit line number is packaged up by splitting it into two 6-bit values. Each 6-bit values is then converted into an 8-bit
value by adding a zero to the start and an odd word parity bit at the end.
Supplementary Data
4.3
The video sequence is made up of lines of data. Each field of data is constructed of the following data lines:
1. A start of frame line
2. 2 of ‘black lines’ (used for black level calibration)
3. 7 (9) of blank lines
4. 292 (288) active video lines
5. An end of frame line
6. 1 (3) blank lines
The numbers given in () are for when the border rows and columns are not output on the databus.
Each line of data starts with an embedded control sequence that identifies the line type (as outlined in Table 3). The
control sequence is then followed by two bytes that, except in the case of the end-of-frame line, contain a coded line
number. The line number sequences starts with the start-of-frame line at 00
H
and increments one per line up until the
end-of-frame line. Each line is terminated with an end-of-line embedded control sequence. The line start embedded
sequences must be used to recognise data lines as a number of null bytes may be inserted between data lines.
Video timing reference and status/configuration data
Parity Checks
Comment
P
3
P
2
P
1
P
0
1
1
1
1
Code word un-corrupted
1
1
1
0
P
0
corrupted, line code OK
1
1
0
1
P
1
corrupted, line code OK
1
0
1
1
P
2
corrupted, line code OK
0
1
1
1
P
3
corrupted, line code OK
0
0
1
0
C
0
corrupted, invert sense of C
0
0
1
0
0
C
1
corrupted, invert sense of C
1
1
0
0
0
C
2
corrupted, invert sense of C
2
All other codes
2-bit error in code word.
Table 6 : Detection of 1-bit and 2-bit errors in the Command Word