saa5250 NXP Semiconductors, saa5250 Datasheet - Page 8

• Manufacturer Part Number: saa5250
• Description: Interface For Data Acquisition And Control For Multi-standard Teletext Systems
• Manufacturer: NXP Semiconductors

Philips Semiconductors
If R04 = 1; the device operates in the fast mode. Prior to writing into the FIFO memory, the CIDAC searches for a start
to a page which is variable due to the different prefixes:
R1 register
Table 4 R1 Register contents
Note
1. X = don’t care
If VAL IN/SYNC = 1; the line signal immediately produces a validation signal for the framing code detection.
If VAL OUT = 0; the line signal is used as a starting signal for an internally processed validation signal (see Fig.15). The
framing code window width is fixed at 13 clock periods and the delay is determined by the contents of the R5 register
(R56 to R50).
At any moment the user is able to ensure that the framing code window is correctly located. This is accomplished by the
VAL OUT pin reflecting the internal validation signal. A CBB signal with programmable width (see section ‘R7 register’)
can also be generated, this is used as a data slicer reset pulse by the SAA5230. The line signal is used as the starting
point of the internal CBB signal width fixed by the contents of the R7 register.
If R16 = 0; then bits R15 and R14 provide the format table number using DIDON long and short prefixes (see Table 6).
If R16 = 1; then the format is determined by the contents of the R3 register.
The bits R13 to R10 represent the first channel number to be checked in the prefix. In U.K. teletext mode only 3 bits are
required, so R13 = X.
January 1987
R17
VAL IN/SYNC
1 = VAL
0 = SYNC
DIDON (long, medium and short): using the redundant bytes, SOH RS, X RS and SOH X (where X is a bit affected by
a parity error)
NABTS, the least significant bit of the PS byte is set to 1
U.K. teletext, ROW = 0
Interface for data acquisition and control
(for multi-standard teletext systems)
R16 TO R14
FORMAT TABLE
000 = list 1
001 = list 2
010 = list 3
011 = list 4
1XX = maximum/default value used (R3)
(1)
8
R13 TO R10
CHANNEL NUMBERS (FIRST DIGIT)
first digit hexadecimal value
Product specification
SAA5250