saa5250 NXP Semiconductors, saa5250 Datasheet - Page 7

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

Philips Semiconductors
Register organization
R0 register
Table 3 R0 Register contents
All of the bytes (see Fig.3) are Hamming protected. The hatched bytes are always stored in the memory in order to be
processed by the CPU (see section ‘Prefix processing’). In the mode without prefix all of the bytes which follow the
framing code are stored in the memory until the end of the data packet, the format is then determined by the contents of
the R3 register.
If R03 = 0; no parity control is carried out and the 8-bits of the incoming data bytes are stored in the fifo memory.
If R03 = 1; the 8th bit of the bytes following the prefix (data bytes) represents the result of the odd parity control.
If R04 = 0; the device operates in the slow mode. The CIDAC retrieves data from the user selected magazine (see
section ‘R1 and R2’) and without searching for a start to a page stores the data into the FIFO memory.
January 1987
handbook, full pagewidth
Interface for data acquisition and control
(for multi-standard teletext systems)
CEEFAX
medium
NABTS
DIDON
DIDON
R04
SLOW/FAST MODE
0 = slow mode
1 = fast mode
DIDON
short
long
FC
FC
FC
FC
FC
A1
A1
A1
A
R03
PARITY
0 = no parity control
1 = odd parity
Fig.3 Five prefixes.
MRAG
format
A2
A2
A2
7
magazine and row address group
A3
A3
CI
CI
R02 TO R00
USED PREFIXES
000 = DIDON long
001 = DIDON medium
010 = DIDON short
011 = not used
100 = U.K. teletext
101 = NABTS
110 = without prefix
111 = without prefix
Product specification
format
SAA5250
PS
MGH077