When I was in high school, I had a teacher that insisted that light dimming was too difficult a task for a student such as I to tackle.
Thus challenged I spent quite a bit of time learning and understanding phase based light dimming using triacs, and programming the 16C84 from microchip to perform this feat. I ended up with this assembly code:
'There are 120 half-cycles in a 60Hz AC waveform
'We want to be able to trigger a triac at any of 256
'points inside each half-cycle. So:
'1 Half cycle takes 8 1/3 mS
'1/256 of one half cycle takes about 32.6uS
'The Pause function here waits (34 * 0xD)uS, plus 3uS overhead
'Overhead includes CALL PAUSE.
'This was originally assembled using Parallax's "8051 style"
'assembler, and was not optimized any further. I suppose
'it could be modified to be closer to 32 or 33uS, but it is
'sufficient for my testing purposes.
movlw 0xFD '11111101
tris 0x5 'Port A
movlw 0xFF '11111111
tris 0x6 'Port B
WaitLow: 'Wait for zero-crossing start
btfss 0x5,0x0 'Port A, Bit 1
goto WaitLow 'If high, goto WaitLow
WaitHigh: 'Wait for end of Zero Crossing
btfsc 0x5,0x0 'Port A, Bit 1
goto WaitHigh 'If low, goto waitHigh
call Pause 'Wait for 0xD * 34 + 3 uS
bcf 0x5,0x1 'Put Low on port A, Bit 1
movlw 0x3 'Put 3 into W
movwf 0xD 'Put W into 0xD
call Pause 'Call Pause, 105 uS
bsf 0x5,0x1 'Put High on Port A, Bit 1
decf 0xE 'Decrement E
movf 0x6,W 'Copy Port B to W
movwf 0xD 'Copy W to 0xD
goto Start 'Wait for zero Crossing
Pause: 'This pauses for 0xD * 34 + 3 Micro Seconds
'Our goal is approx. 32 uS per 0xD
'But this is close enough for testing
movlw 0xA 'Move 10 to W
movwf 0xC 'Move W to 0xC
decfsz 0xC 'Decrement C
goto Label1 'If C is not zero, goto Label1
decfsz 0xD 'Decrement D
goto Pause 'If D is not zero, goto Pause
Of course you'd need to modify this for the chip you mention, and maybe add a cheap serial routine for input since your chip doesn't have an 8 bit wide port to listen to, but the idea is that a seemingly complex job can be done in very little code - you can fit ten copies of the above program into the 10F200.
You can find more project information on my Light Dimming page. Incidentally I never did show this to my teacher, but did end up doing a number of lighting rigs for my DJ friend.