SAA5244A Datasheet, PDF (17/32 Pages) NXP Semiconductors – Integrated VIP and teletext decoder IVT1.1

Philips Semiconductors
Integrated VIP and teletext decoder
(IVT1.1)
Product specification
SAA5244A
SAA5244A page memory organization
The organization of the page memory is shown in Fig.9. 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.
7 characters
for status
7
1
fixed character
written by IVT hardware
alphanumerics white for normal
alphanumerics green when looking
for display page
24
24 characters from page header
rolling when display page looked for
8 characters
always rolling
(time)
ROW
8
0
1
2
3
4
MAIN PAGE DISPLAY AREA
5
to
20
PACKET X / 22
PACKET X / 23
PACKET X / 24 STORED HERE IF R0D7 = 1
10
14
10 bytes for
received
page information
14 bytes
free for use
by microcontroller
21
22
23
24
25
MBA274
Fig.9 Basic page memory organization.
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 SAA5244A 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 1. The remaining 14
bytes are free for use by the microcomputer.
PACKET X / 24 if R0D7 = 0
PACKET X / 27 / 0
PACKETS 8 / 30 / 0 to 15
ROW
0
1
2
MBA275 - 2
Fig.10 Organization of the extension memory.
March 1992
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