LM1247 National Semiconductor, LM1247 Datasheet - Page 35

• Manufacturer Part Number: LM1247
• Description: 150 MHz I2C Compatible RGB Preamplifier with Internal 512 Character OSD ROM, 512 Character RAM and 4 DACs
• Manufacturer: National Semiconductor

Control Register Definitions
Display Window 1 Horizontal Start Position:
Display Window 1 Vertical Start Position:
Display Window 1 Start Address:
Display Window 1 Column Width:
X
Bits 7–0
Bits 7–0
Bits 8–0
Bits 15–9
Bits 31–0
X
There are two possible OSD windows which can be displayed simultaneously or individually. This
register determines the horizontal start position of Window 1 in OSD pixels (not video signal
pixels). The actual position, to the right of the horizontal flyback pulse, is determined by multiplying
this register value by 4 and adding 30. Due to pipeline delays, the first usable start location is
approximately 42 OSD pixels following the horizontal flyback time. For this reason, we recommend
this register be programmed with a number larger than 2, otherwise improper operation may result.
This register determines the Vertical start position of the Window 1 in constant-height character
lines (not video scan lines). The actual position is determined by multiplying this register value by
2. (Note: each character line is treated as a single auto-height character pixel line, so multiple scan
lines may actually be displayed in order to maintain accurate position relative to the OSD character
cell size. See the Constant Character Height Mechanism section.) This register should be set so
the entire OSD window is within the active video.
This register determines the starting address of Display Window 1 in the Display Page RAM. The
power-on default of 0x00 starts Window 1 at the beginning of the Page Ram (0x8000). This
register is new for the LM1247 and allows Window 1 to start anywhere in the Page RAM rather
than just at 0x8000. Note that the address this points to in Page RAM must always contain the SL
code for the first line of Window 1.
These bits are reserved and should be set to zero.
COLWIDTH1B1 (0x8415)
These are the Display Window 1 Column Width 2x Enable Bits. These thirty-two bits correspond to
columns 31–0 of Display Window 1, respectively. A value of zero indicates the column will have
normal width (12 pixels). A “1” indicates the column will be twice as wide as normal (24 pixels).
For the double wide case, each Character Font pixel location will be displayed twice, in two
consecutive horizontal pixel locations. The user should note that if more than 32 display characters
are programmed to reside on a line, then all display characters after the first thirty-two will have
normal width (12 pixels).
COLWIDTH1B3 (0x8417)
W1STRTADRH (0x8413)
X
Reserved
X
X
Window 1 Column Width - High Bytes
Window 1 Column Width - Low Bytes
X
Window 1 Horizontal Start Position
Window 1 Vertical Start Position
(Continued)
X
HSTRT1 (0x8410)
VSTRT1 (0x8411)
COL[31:16]
COL[15:0]
1H[7:0]
1V[7:0]
35
Window 1 Start Address
COLWIDTH1B2 (0x8416)
COLWIDTH1B0 (0x8414)
W1STRTADRL (0x8412)
1AD[8:0]
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