SAA55XX Datasheet, PDF (38/84 Pages) NXP Semiconductors – TV microcontrollers with Closed Captioning (CC) and On-Screen Display (OSD)

Philips Semiconductors
TV microcontrollers with Closed Captioning (CC)
and On-Screen Display (OSD)
Preliminary specification
SAA55xx
16.3 Addressing memory
The memory can be addressed by the microcontroller in
two ways, either directly using a MOVX command, or via
Special Function Registers depending on what address is
required.
The dedicated Auxiliary RAM, and Display memory in the
range 8000H to 84FFH, can only be accessed using the
MOVX command.
The Display memory in the range 2000H to 23FFH can
either be directly accessed using the MOVX, or via the
Special Function Registers.
16.4 Page clearing
Page clearing is performed on request from the
microcontroller under the control of the embedded
software.
At power-on and reset the Text Display memory (from
2000H to 23FFH) is cleared to the value of 20H.
The TXT13.PAGE CLEARING bit will be set while this
takes place.
16.4.1 DATA CAPTURE PAGE CLEAR
Not present in the SAA55xx OSD only devices.
16.3.1 TXT DISPLAY MEMORY SFR ACCESS
The Display memory when in TXT mode (see Fig.14) is
configured as 40 columns wide by 25 rows and occupies
1K × 8 bits of memory. The row and column is selected
using TXT9.R<4:0> and TXT10.C<5:0>. The data at the
selected position can be read or written using
TXT11.D<7:0>.
Whenever a read or write is performed on TXT11, the row
values stored in TXT9 and column value stored in TXT10
are automatically incremented. For rows 0 to 24 the
column value is incremented up to a maximum of 39, at
which point it resets to a logic 0 and increments the row
counter value. When row 25 column 23 is reached the
values of the row and column are both reset to logic 0.
Writing values outside of the valid range for TXT9 or
TXT10 will cause undetermined operation of the
auto-incrementing function for accesses to TXT11.
16.4.2 SOFTWARE PAGE CLEAR
The software can also initiate a page clear, by setting the
TXT9.CLEAR MEMORY bit. The CLEAR MEMORY bit is
not latched so the software does not have to reset it after
it has been set.
Only one page can be cleared in a TV line so if the
software requests a page clear it will be carried out on the
next TV line on which the Data Capture hardware does not
force the page to be cleared. A flag, TXT13.PAGE
CLEARING, is provided to indicate that a software
requested page clear is being carried out. The flag is set
when a logic 1 is written into the TXT9.CLEAR MEMORY
bit and is reset when the page clear has been completed.
Inventory page clearing in not present in the SAA55xx
OSD only devices.
16.3.2 TXT DISPLAY MEMORY MOVX ACCESS
It is important for the generation of OSD displays, that use
this mode of access, to understand the mapping of the
MOVX address onto the display row and column value.
This mapping of row and column onto address is shown in
Table 10. The values shown are added onto a base
address for the required memory block (see Fig.13) to give
a 16-bit address.
Table 10 Column and row to MOVX address (lower 10 bits of address)
ROW
Row 0
Row 1
...
Row 23
Row 24
Row 25
COL.0
000H
020H
...
2E0H
300H
320H
...
COL.23
...
COL.31
...
017H
...
01FH
...
037H
...
03FH
...
...
...
...
...
3F7H
...
2FFH
...
317H
...
31FH
...
337H
...
COL.32
...
COL.39
3F8H
...
3FFH
3F0H
...
3F7H
...
...
...
340H
...
347H
338H
...
33FH
...
2000 Feb 23
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