LM1253A National Semiconductor, LM1253A Datasheet - Page 42

• Manufacturer Part Number: LM1253A
• Description: Monolithic Triple 180 MHz I2C CRT Pre-amp With Integrated Analog On Screen Display (OSD) Generator
• Manufacturer: National Semiconductor

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Control Register Definitions
ROM Signature Control Register (I
REGISTER NAME: ROMSIGCTRL
Bit 0:
Bits 7–1:
ROM Signature Data Register (I
REGISTER NAME: ROMSIGDATAB1 (840Fh) ROMSIGDATAB0 (840Eh)
Bit 15
CRC15 CRC14 CRC13 CRC12 CRC11 CRC10
Bits 15–0: ROM Signature Data. This register indicates the residual value from the CRC calculation. Devices containing ROMs
Display Window 1 Horizontal Pixel Start Location Register (I
REGISTER NAME: HSTRT1 (8410h)
Bit 7
Bits 7–0: Display Window 1 Horizontal Pixel Start Location. These seven bits determine the starting horizontal pixel location,
Display Window 1 Vertical Pixel Start Location Register (I
REGISTER NAME: VSTRT1 (8411h)
Bit 7
Bits 7–0: Display Window 1 Vertical Pixel Start Location. These eight bits determine the starting vertical pixel location in con-
Display Window 1 Column Width Control Register (I
REGISTER NAME: COLWIDTH1B3 (8417h) COLWIDTH1B2 (8416h) COLWIDTH1B1 (8415h) COLWIDTH1B0 (8414h)
Bit 31
Bit 15
Bits 31–0: Display Window 1 Column Width 2x Enable Bits. These thirty-two bits correspond to columns 31–0 of Display Win-
COL31 COL30 COL29 COL28 COL27 COL26 COL25 COL24 COL23 COL22 COL21 COL20 COL19 COL18 COL17 COL16
COL15 COL14 COL13 COL12 COL11 COL10
Bit 7
RSV
1H7
1V7
RSV
1H6
1V6
which is determined by multiplying the value of these bits by 4 and adding 30 pixels. Due to pipeline delays, the first
usable location for the OSD window is approx 42 pixels to the right of the horizontal flyback pulse. For this reason, the
display start location must be programmed with a number larger than 2, otherwise improper operation may occur.
This byte must be set so the entire OSD window is within the active video.
stant height character lines, which is determined by multiplying the value of these bits 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 main-
tain accurate position relative to the character cell size — See Constant Character Height Mechanism section.)
This byte must be set so the entire OSD window is within the active video.
Calculate ROM Signature. Setting this bit causes the entire ROM to be read, sequentially, and a 16 bit CRC calculated
over its contents. The residual value from this calculation is placed in the ROM Signature Data register. This bit au-
tomatically clears itself when the calculation has been completed.
RESERVED.
with different programming will give different signatures. Devices with the same ROM programming will give the same
signature.
dow 1, respectively. A value of zero indicates the column will have normal width (12 pixels). A value of one 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 row, then all display
characters after the first thirty-two will have normal width (12 pixels).
RSV
1H5
1V5
RSV
1H4
1V4
RSV
1H3
1V3
2
C address 840Eh–840Fh).
2
C address 840Dh).
RSV
1H2
1V2
RSV
1H1
1V1
(Continued)
CRC9
COL9
CRS
2
1H0
1V0
Bit 0
Bit 0
Bit 0
C address 8414h–8417h).
CRC8
Bit 24
COL8
Bit 8
Bit 8
2
42
C address 8411h).
2
CRC7
Bit 23
C address 8410h).
COL7
Bit 7
Bit 7
CRC6
COL6
CRC5
COL5
CRC4
COL4
CRC3
COL3
CRC2
COL2
CRC1
COL1
CRC0
COL0
Bit 0
Bit 16
Bit 0