SAA5X9X Datasheet, PDF (29/68 Pages) NXP Semiconductors – Economy teletext and TV microcontrollers

Philips Semiconductors
Economy teletext and TV microcontrollers
Preliminary specification
SAA5x9x family
8.6 Memory organisation of SAA5296/7,
SAA5296/7A and SAA5496/7
The teletext memory is divided into 10 blocks. Normally,
when the TXT1.EXT PKT OFF bit is logic 0, each of blocks
0 to 8 contains a teletext page arranged in the same way
as the basic page memory (see Fig.6) of the page device
and block 9 contains extension packets (see Fig.7).
When the TXT1.EXT PKT OFF bit is logic 1, no extension
packets are captured and block 9 of the memory is used to
store another page.
The number of the memory block into which a page is
written corresponds to the page request number which
resulted in the capture of the page.
Packet 0, the page header, is split into 2 parts when it is
written into the text memory. The first 8 bytes of the header
contain control and addressing information. They are
Hamming decoded and written into columns 0 to 7 of
row 25 (see Table 15). Row 25 also contains the
magazine number of the acquired page and the PBLF flag
but the last 14 bytes are unused and may be used by the
software, if necessary. The Hamming error flags are set if
the on-board 8/4 Hamming checker detects that there has
been an uncorrectable (2 bit) error in the associated byte.
It is possible for the page to still be acquired if some of the
page address information contains uncorrectable errors if
that part of the page request was a ‘don’t care’. There is no
error flag for the magazine number as an uncorrectable
error in this information prevents the page being acquired.
The interrupted sequence (C9) bit is automatically dealt
with by the acquisition section so that rolling headers do
not contain discontinuities in the page number sequence.
The magazine serial (C11) bit indicates whether the
transmission is a serial or a parallel magazine
transmission. This affects the way the acquisition section
operates and is dealt with automatically.
The newsflash (C5), subtitle (C6), suppress header (C7),
inhibit display (C10) and language control (C12 to 14) bits
are dealt with automatically by the display section,
described below.
The update (C8) bit has no effect on the hardware. The
remaining 32 bytes of the page header are parity checked
and written into columns 8 to 39 of row 0. Bytes which
pass the parity check have the MSB set to a logic 0 and
are written into the page memory. Bytes with parity errors
are not written into the memory.
Table 14 Notation used in Table 15
MNEMONIC
MAG
PT
PU
HT
HU
MT
MU
DESCRIPTION
Magazine
Page Tens
Page Units
Hours Tens
Hours Units
Minutes Tens
Minutes Units
Table 15 The data in row 25 of the basic page memory
COL
0
1
2
3
4
5
6
7
8
9
10 to 23
BIT 7
0
0
0
0
0
0
0
0
0
0
−
BIT 6
0
0
0
0
0
0
0
0
0
0
−
BIT 5
0
0
0
0
0
0
0
0
0
PBLF
−
BIT 4
Hamming error
Hamming error
Hamming error
Hamming error
Hamming error
Hamming error
Hamming error
Hamming error
FOUND
0
unused
BIT 3
PU3
PT3
MU3
C4
HU3
C6
C10
C14
0
0
−
BIT 2
PU2
PT2
MU2
MT2
HU2
C5
C9
C13
MAG2
0
−
BIT 1
PU1
PT1
MU1
MT1
HU1
HT1
C8
C12
MAG1
0
−
BIT 0
PU0
PT0
MU0
MT0
HU0
HT0
C7
C11
MAG0
0
−
1997 Jul 07
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