Taking into account the picture below (from an article by Martin Hinner) we noticed that the lines 3, 6 and 9 from an interlaced signal are different from the first to the second field.

But it is is possible to make a tweak so the same code for generating the equalization pulses and the vertical serration in both fields. The tweak here is to generate only half of the line 263 from first field then stretch line 9 from the second field so the end we have a correct interlaced signal.

Then the generation of signals might follow the following order

; == FIRST FRAME, 262 lines ==
; lines 
;   3      Heq   - Horizontal Equalization Lines
;   3      Vser  - Vertical Serration Lines
;   3      Heq   - Horizontal Equalization Lines
;  10      Blank - Top Blanking lines
;  24      TBord - Top Border lines
; 200      Vis   - Visible lines, field 1
;                  30 - progressive  greyscale
;                  40 - resolution + progress greyscale
;                  30 - progressive  greyscale
;
;                  30 - decrescent  greyscale
;                  40 - resolution + decrescent greyscale
;                  30 - decrescent  greyscale
;
;  21      BBord - Bottom Border lines
;
; == SECOND FRAME, 263 lines ==
; 1/2      half1 - first half line (half blank line)
;   3      Heq   - Horizontal Equalization Lines
;   3      Vser  - Vertical Serration Lines
;   3      Heq   - Horizontal Equalization Lines
; 1/2      half2 - second half line (shelf)
;  10      Blank - Top Blanking lines
;  24      TBord - Top Border lines
; 200      Vis   - Visible lines, field 2
;                  30 - progressive  greyscale
;                  40 - resolution + progress greyscale
;                  30 - progressive  greyscale
;
;                  30 - decrescent  greyscale
;                  40 - resolution + decrescent greyscale
;                  30 - decrescent  greyscale
;
;  21      BBord - Bottom Border lines
;------
; 525 lines 

This might not look Canonical but it absolutely works!