saa5250 NXP Semiconductors, saa5250 Datasheet - Page 14

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

Philips Semiconductors
Table 14 Hamming correction (decoding)
Note
1. A = B8
part 1
A format transcoder produces a 6-bit code (up to 63) and uses the following as inputs:
part 2
A format counter operating at the character clock frequency which receives the 6-bit code from the format transcoder and
is used to check the data packet length following the prefix.
Serial/parallel converter
The serial/parallel converter consists of three parts:
January 1987
Format processing
The format processing consist of two parts:
DIDON long and short prefixes;
Other prefixes (R16 = 1)
6-bit maximum/default format (see section ‘R3 register’)
An 8-bit shift register which receives the SD input and operates at the bit frequency (DCK).
An 8-bit parallel register used for storage.
A framing code detection circuit. This logic circuit compares the 8-bits of the R4 register with that of the serial register.
If seven bits out of eight match (in coincidence with a validation window), it produces a start signal for a new teletext
data line to the sequence controller.
Interface for data acquisition and control
(for multi-standard teletext systems)
B = B8
C = B6
D = B8
hamming corrected code (4-bits)
accept/reject code condition
table number (see section ‘R1 register’, bits R15 and R14)
= exclusive OR gate function
A
1
0
1
0
1
1
1
0
0
B6
B4
B5
B7
A.B.C = 0
B2
B3
B4
B6
B
1
0
1
1
1
0
0
0
1
B1
B2
B2
B5
B4
B3
C
1
1
1
0
0
0
1
0
1
B2
B1
D
1
0
0
0
0
0
0
0
0
1
14
INTERPRETATION
no error
error on B8
error on B7
error on B6
error on B5
error on B4
error on B3
error on B2
error on B1
multiple errors
INFORMATION
accepted
corrected
accepted
corrected
accepted
corrected
accepted
corrected
accepted
rejected
Product specification
SAA5250