TV Out Question...
bmb!
Posts: 26
I've read the book and searched the forums, so I hope this hasn't been asked hundred times before....
I understand the 3-bit DAC for the composite video out but do I need the 4th resistor for the "aural subcarrier". I'm just stumped by the note on the schematic... "This resistor is only required for aural subcarrier in broadcast mode" What is that? And do I want it? If possible I wouldn't mind leaving that pin free for other uses...
Thanks, in advance for the help...
I understand the 3-bit DAC for the composite video out but do I need the 4th resistor for the "aural subcarrier". I'm just stumped by the note on the schematic... "This resistor is only required for aural subcarrier in broadcast mode" What is that? And do I want it? If possible I wouldn't mind leaving that pin free for other uses...
Thanks, in advance for the help...
Comments
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JMH
as my first stuff was just the three pins, so if you're connecting direct to composite, then you don't need the fourth resistor and pin.
be aware though to remove that pin dir activity from any tv display driver you use, as that may cause you problems when you're not expecting it, trying to debug some unexpected data coming out of the port. [noparse]:)[/noparse]
Post Edited (Baggers) : 12/18/2007 4:06:26 PM GMT
Paul
I'm reading through TV.SPIN now to see what I need to to to recover my pin 15
Paul
It is also little known, that the Video Logic outputs on EIGHT pins by default! However 4 (or 5) of them are generally suppressed by your settings.
'' tv_pins '' '' bits 6..4 select pin group: '' %000: pins 7..0 '' %001: pins 15..8 '' %010: pins 23..16 '' %011: pins 31..24 '' %100: pins 39..32 '' %101: pins 47..40 '' %110: pins 55..48 '' %111: pins 63..56 '' '' bits 3..0 select pin group mode: '' %0000: %0000_0111 - baseband '' %0001: %0000_0111 - broadcast '' %0010: %0000_1111 - baseband + chroma '' %0011: %0000_1111 - broadcast + aural '' %0100: %0111_0000 broadcast - '' %0101: %0111_0000 baseband - '' %0110: %1111_0000 broadcast + aural - '' %0111: %1111_0000 baseband + chroma - '' %1000: %0111_0111 broadcast baseband '' %1001: %0111_0111 baseband broadcast '' %1010: %0111_1111 broadcast baseband + chroma '' %1011: %0111_1111 baseband broadcast + aural '' %1100: %1111_0111 broadcast + aural baseband '' %1101: %1111_0111 baseband + chroma broadcast '' %1110: %1111_1111 broadcast + aural baseband + chroma '' %1111: %1111_1111 baseband + chroma broadcast + aural '' ----------------------------------------------------------- '' active pins top nibble bottom nibble '' '' the baseband signal nibble is arranged as: '' bit 3: chroma signal for s-video (attach via 560-ohm resistor) '' bits 2..0: baseband video (sum 270/560/1100-ohm resistors to form 75-ohm 1V signal) '' '' the broadcast signal nibble is arranged as: '' bit 3: aural subcarrier (sum 560-ohm resistor into network below) '' bits 2..0: visual carrier (sum 270/560/1100-ohm resistors to form 75-ohm 1V signal)▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
JMH