saa5281 NXP Semiconductors, saa5281 Datasheet - Page 16

• Manufacturer Part Number: saa5281
• Description: Integrated Video Input Processor And Teletext Decoder Ivt1.8
• Manufacturer: NXP Semiconductors

Philips Semiconductors
ON-CHIP MEMORY
Page memory organization
The organization of the page memory is illustrated by Fig.9. The IVT1.8* 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 the extra row available for software generated status messages and FLOF/FASTEXT prompt
information.
R
Row 0
Row 0 is for the page header. The first seven characters
(0 to 6) are free for status messages. Character 8 is an
alphanumeric white or green control character, written
automatically by IVT1.8* to give a green rolling header
when a page is being looked for. The last eight characters
are for rolling time.
1996 Nov 04
handbook, full pagewidth
EMARK TO
Integrated Video input processor and
Teletext decoder (IVT1.8*)
Fig.9
7 characters
for status
page information
10 bytes for
received
7
10
Fig.9 Basic page memory organization.
PACKET X / 24 STORED HERE IF R0D7 = 1
1
24 characters from page header
rolling when display page looked for
written by IVT hardware:
alphanumerics white for normal;
alphanumerics green when looking
for display page
MAIN PAGE DISPLAY AREA
if enabled 14 bytes reserved in
fixed character
chapter 5 for VPS data
PACKET X / 22
PACKET X / 23
14
16
24
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 microcomputer.
always rolling
8 characters
(time)
MBD789
8
ROW
20
21
22
23
24
25
to
0
1
2
3
4
5
Preliminary specification
SAA5281