saa5254 NXP Semiconductors, saa5254 Datasheet - Page 14

• Manufacturer Part Number: saa5254
• Description: Integrated Vip And Teletext Decoder Ivt1.1x
• Manufacturer: NXP Semiconductors

Philips Semiconductors
ON-CHIP MEMORY
SAA5254 page memory organization
The organization of the page memory is shown in Fig.7. The device provides an additional row as compared with first
generation decoders; this brings the display format up to 40 characters by 25 rows. Rows 0 to 23 form the teletext page;
Row 24 is available for software generated status messages and FLOF/FASTEXT prompt information.
1996 Nov 07
Integrated VIP and teletext decoder
(IVT1.1X)
Fig.8 Organization of the extension memory.
PACKET X / 24 if R0D7 = 0
PACKET X / 27 / 0
PACKETS 8 / 30 / 0 to 15
7 characters
for status
page information
MBA275 - 2
10 bytes for
received
7
10
Fig.7 Basic page memory organization.
PACKET X / 24 STORED HERE IF R0D7 = 1
ROW
1
0
1
2
24 characters from page header
rolling when display page looked for
written by IVT hardware
alphanumerics white for normal
alphanumerics green when looking
MAIN PAGE DISPLAY AREA
fixed character
by microcontroller
PACKET X / 22
PACKET X / 23
free for use
14 bytes
14
24
14
for display page
R
Row 0
Row 0 is for the page header. The first seven columns
(0 to 6) are free for status messages. The eighth is an
alphanumeric white or green control character, written
automatically by the SAA5254 to give a green rolling
header when a page is being looked for. The last eight
characters are for rolling time.
Row 25
The first 10 bytes of Row 25 contain control data relating
to the received page as shown in Table 5. The remaining
14 bytes are free for use by the microcontroller.
EMARK TO
Fig.7
always rolling
8 characters
(time)
MBA274
8
ROW
20
21
22
23
24
25
to
0
1
2
3
4
5
Preliminary specification
SAA5254