Minimal NTSC

ntsc.spin

CON
    _CLKMODE = RCSlow     ' Start prop in RCSlow mode internal crystal

PUB main

    clkset(%01101000,  12_000_000)          ' Set internal oscillator to RCFast and set PLL to start
    waitcnt(cnt + 120_000)                  ' wait approx 10ms at 12mhz for PLL to 'warm up'

    clkset(%01101111, 80_000_000)           ' 80MHz (5MHz PLLx16)  
    coginit(COGID, @cogstart, @cogstart)

DAT
            org         0
cogstart
            mov         vcfg, ivcfg         ' Sets up the parameters for video generation
            mov         ctra, ictra         ' internal PLL mode, PLLA = 16 * colorburst frequency
            mov         frqa, ifrqa         ' 2 * colorburst frequency 
            mov         dira, idira         ' Sets pin directions

'-----------------------------------------------------------------------------------------------
'   MAIN LOOP
'-----------------------------------------------------------------------------------------------
mainloop
            mov         numline, #9         ' 9 lines of vsync
vsync0
            cmp         numline, #6     wz  ' lines 4,5,6 serration pulses
    if_nz   cmp         numline, #5     wz  ' lines 1,2,3 / 7,8,9 equalizing pulses
    if_nz   cmp         numline, #4     wz  ' 
            
            mov         count, #2           ' 2 pulses per line
:half
    if_nz   mov         VSCL, vscleqal      ' equalizing pulse (short)
    if_z    mov         VSCL, vsclselo      ' serration pulse (long)
            waitvid     sync, #0            ' -40 IRE
    if_nz   mov         VSCL, vscleqhi      ' equalizing pulse (long)
    if_z    mov         VSCL, vsclsync      ' serration pulse (short)
            waitvid     sync, blank         ' 0 IRE

            djnz        count, #:half
            djnz        numline, #vsync0

            mov         numline, #12        ' 12 blank lines
blank0
            mov         VSCL, vsclsync
            waitvid     sync, #0            ' -40 IRE
            mov         VSCL, vsclblnk
            waitvid     sync, blank         ' 0 IRE
            djnz        numline, #blank0

'-----------------------------------------------------------------------------------------------
'   ACTIVE VIDEO
'-----------------------------------------------------------------------------------------------
            mov         numline, #241       ' 241 lines of active video
active
            mov         VSCL, vsclsync      ' horizontal sync (0H) 4.7us
            waitvid     sync, #0            ' -40 IRE

            mov         VSCL, vscls2cb      ' 5.3us 0H to burst
            waitvid     sync, blank            

            mov         VSCL, vsclbrst      ' 9 cycles of colorburst
            waitvid     sync, burst

            mov         VSCL, vsclbp        ' backporch 9.2us OH to active video
            waitvid     sync, blank
            
'-----------------------------------------------------------------------------------------------
'   VISIBLE SCAN LINE START
'-----------------------------------------------------------------------------------------------
            mov         VSCL, vsclactv      ' PLLA per pixel, pixels per frame

            waitvid     color, pixels
            waitvid     color, pixels
            waitvid     color, pixels
            waitvid     color, pixels
            waitvid     color, pixels
            waitvid     color, pixels
            waitvid     color, pixels
            waitvid     color, pixels

'-----------------------------------------------------------------------------------------------
'   VISIBLE SCAN LINE END
'-----------------------------------------------------------------------------------------------
            mov         VSCL, vsclfp        ' front porch 1.5us
            waitvid     sync, blank
            
            djnz        numline, #active
            jmp         #mainloop
'-----------------------------------------------------------------------------------------------
'   END
'-----------------------------------------------------------------------------------------------

'-----------------------------------------------------------------------------------------------
'   CONFIG DATA
'-----------------------------------------------------------------------------------------------
ivcfg                   long    %0_11_0_0_1_000_00000000000_001_0_01110000      ' 
ictra                   long    %0_00001_110_00000000_000000_000_000000         ' NTSC (PLLDIV = VCO/2, PLL internal (video mode)
ifrqa                   long    $16E8_BA2F                                      ' (7,159,090.9Hz/80MHz)<<32 NTSC demoboard & Hydra 
idira                   long    $0000_7000                                      ' demoboard

sync                    long    $8A0200                                         ' %%0 = -40 IRE, %%1 = 0 IRE, %%2 = burst
							                  ' 0000 0000 1000 1010 0000 0010 0000 0000
blank                   long    %%1111_1111_1111_1111                           ' 16 pixels color 1
burst                   long    %%2222_2222_2222_2222                           ' 16 pixels color 1

vscleqal                long    1<<12+135               ' NTSC sync/2
vsclsync                long    1<<12+269               ' NTSC sync = 4.7us
vsclblnk                long    1<<12+3369              ' NTSC H-sync
vsclselo                long    1<<12+1551              ' NTSC H/2-sync
vscleqhi                long    1<<12+1685              ' NTSC H/2-sync/2
vscls2cb                long    1<<12+304-269           ' NTSC sync to colorburst
vsclbrst                long    16<<12+16*9             ' NTSC 16 PLLA per cycle, 9 cycles of colorburst
vsclbp                  long    1<<12+(527-304-16*9)+213' NTSC back porch + overscan (213)
vsclactv                long    10<<12+10*32            ' NTSC 10 PLLA per pixel, 32 pixels per frame
vsclfp                  long    1<<12+214+86            ' NTSC overscan (214) + front porch

numline                 long    $0
count                   long    $0


color                   long    $02, $38, $02, $38
pixels                  long    %10101010_10101010_10101010_10101010