Ciro, you have to set the capture card video settings the same as the output of the VCR does. VCR typically outputs pure NTSC (3.58Mhz or 4.43Mhz) or it transform the NTSC signal into PAL (3.58Mhz or 4.43 Mhz) for better compatibiltiy.
Even if the tape is NTSC that doesn't mean that the VCR outputs pure NTSC. In the VCR manual you will find information how the VCR outputs NTSC tapes.
Do you capture via Cinch (Yellow/Red/White) or Antenna (don't do that)?
Usually in the settings you have stuff like: PAL-G/PAL-B, PAL-60, NTSC 4.43 Mhz, NTSC 3.58 Mhz, 720x480 (NTSC Output) or 720x576 (PAL Output), 25 fps or 30fps (->50/60 interlaced).
Anyone that comes to the european TI Treffen of this year and wants to update, I can bring my laptop with xilinx software and the JTAG programmer cable. All you need is your F18A chip and a powered ti99 mainboard. Just remind me on the cable before the Meeting, best via private message or mail.
Btw: The mimimised funnelweb version -included in your XB compiler for compiling the assembler source file - doesn't work with CF7+/NanoPEB devices. Funnelweb as such doesn't like the CF7+/NanoPEB. There exists a modified Funnelweb version that is compatible, but I don't have it. Maybe you can point that iisue in the docu and/or the menu screen.
Since a lot of people that work on real hardware are using the CF7+/NanoPEB, this should get pointed out.
I don't understand why you would need each routine as a dedicated file on the disk if you want to go for an approach, where you only load those routines into RAM which are used by the program?