
Bt848/848A/849A
Single-Chip Video Capture for PCI
Brooktree
94
C
ONTROL
R
EGISTER
D
EFINITIONS
Vertical Delay Register, Lower Byte
L848A_A
Vertical Delay Register, Lower Byte
Memory Mapped Location 0x010 – Even Field (E_VDELAY_LO)
Memory Mapped Location 0x090 – Odd Field (O_VDELAY_LO)
Upon reset it is initialized to 0x16. VDELAY_LO(0) is the least significant bit. This 8-bit register is the lower byte of
the 10-bit VDELAY register. The two MSBs of VDELAY are contained in the CROP register. VDELAY defines the
number of half lines between the trailing edge of VRESET and the start of active video.
Vertical Active Register, Lower Byte
Memory Mapped Location 0x014 – Even Field (E_VACTIVE_LO)
Memory Mapped Location 0x094 – Odd Field (O_VACTIVE_LO)
Upon reset it is initialized to 0xE0. VACTIVE_LO(0) is the least significant bit. This 8-bit register is the lower byte
of the 10-bit VACTIVE register. The two MSBs of VACTIVE are contained in the CROP register. VACTIVE defines
the number of lines used in the vertical scaling process.
Horizontal Delay Register, Lower Byte
Memory Mapped Location 0x018 – Even Field (E_DELAY_LO)
Memory Mapped Location 0x098 – Odd Field (O_DELAY_LO)
Upon reset it is initialized to 0x78. HDELAY_LO(0) is the least significant bit. This 8-bit register is the lower byte
of the 10-bit HDELAY register. The two MSBs of HDELAY are contained in the CROP register. HDELAY defines
the number of scaled pixels between the falling edge of HRESET and the start of active video.
Bits
Type
Default
Name
Description
[7:0]
RW
0x16
VDELAY_LO
The least significant byte of the vertical delay register.
Bits
Type
Default
Name
Description
[7:0]
RW
0xE0
VACTIVE_LO
The least significant byte of the vertical active register.
Bits
Type
Default
Name
Description
[7:0]
RW
0x78
HDELAY_LO
The least significant byte of the horizontal delay register. HACTIVE
pixels will be output by the chip starting at the fall of HRESET.