Programming Model
4.1.13 Horizontal Interlace Register (HIR): Address 87I3
This register must be programmed if an interlaced sync. display is required. Otherwise it may be ignored. It defines the position oŁ the VSYNC pulses in the odd field, and as such defines the offset of the odd and even fields. It should normally be programmed to be half way along a raster, so if value L is written into the HCR, then value L/2 should be written into the HIR
This is a 14 bit register of which the bottom bit must be programmed to 0.
31 30 29 28 27 26 26 24 23 22 21 20 19 16 17 16 16 14 13 12 11 10 9 6 7 6 6 4 3 2 1 0
7 0 0 010 1 1 1	x x z x x x x x x xx x x 0 1
HIR value
4.1.14 Horizontal Test Registers: Addresses 88H & SCH
Two registers are provided for testing the chip in production. Neither of these registers are intended to be used during normal operation of the device. Writing a 14 bit value to address SSH writes that value into the horizontal counter immediately.
Writing a 14 bit value to address 8CH writes that value into all the horizontal registers simultaneously. 4.1.15 Vertical Cycle Register (VCR): Address 90H
This 13 bit register defines the period, in units of a raster, of the vertical scan. i.e. display time + flyback time. If N rasters are required in a complete frame, then value (N-2) should be programmed into the VCR.
If an interlaced display is selected, (N-3)/2 must be programmed into the VCR. [N must be odd]. Here N is still the number of rasters in a complete frame, not a field.
31 30 29 26 27 26 25 24 23 22 21 20 19 16 17 16 15 14 13 12 11 70 9 8 7 6 5 4 3 2 1 0 1 0 0 1 0 0 0 0	% X % % % X X X X X X X X X
VCR value
4.1.16 Vertical Sync Width Register (VSWR): Address 91H
This 13 bit register defines the width, in units of a raster, of the VSYNC pulse.
If N rasters are required in the VSYNC pulse, then value (N-1) should be programmed into the VSWR. The minimum value allowed for N is 1.
31 30 29 28 27 26 26 24 23 22 21 20 19 16 17 16 15 14 13 12 11 10 9 6 7 6 5 4 3 2 1 0 0 0 1 0 0 0 1	X % X X X % X X X X X X X I
VSWR value
21