lidnariq wrote:I think I'm satisfied with the VRC now, so it'd be lovely if you could determine the connectivity of the 74'139...
74LS139 Dual 2-Line to 4-Line Decoder / Demultiplexer
Pin 1 /1Enable: Pin 11
Pin 2 1Da: PRG1 and PRG2 A12 (Pin 2)
Pin 3 1Db: CPU A13 (Pin 17)
Pin 4 /1Y0: NC
Pin 5 /1Y1: (127) Pin 20
Pin 6 /1Y2: NC
Pin 7 /1Y3: NC
Pin 8 GND: GND
Pin 9 /2Y3: NC
Pin 10 /2Y2: NC
Pin 11 /2Y1: Pin 1
Pin 12 /2Y0: NC
Pin 13 2Db: 74HC00 Y3 (Pin 8)
Pin 14 2Da: NC
Pin 15 /2Enable: (127) Pin 22
Pin 16 VCC: +5V
lidnariq wrote:... the two 74'00s ...
There is a 74HC00 and a 74HC08...
74HC00P Quadruple 2-input Positive NAND Gate
Pin 1 A1: GND
Pin 2 B1: GND
Pin 3 Y1: NC
Pin 4 A2: NC
Pin 5 B2: 74LS139 2Db (13) + CPU A15 (19)
Pin 6 Y2: 108 (10)
Pin 7 GND: GND
Pin 8 Y3: 127 (22) + 74LS139 /2E (Pin 15)
Pin 9 A3: CPU (31) Bridged to Pin 10
Pin 10 B3: CPU (31) Bridged to Pin 9
Pin 11 Y4: PRG1 (20)
Pin 12 A4: PRG2 (20) Bridged to Pin 13
Pin 13 B4: PRG2 (20) Bridged to Pin 12
Pin 14 Vcc: +5V
M74HC08P Quadruple 2-input Positive AND Gate
Pin 1 A1: GND
Pin 2 B1: GND
Pin 3 Y1:
Pin 4 A2: GND
Pin 5 B2: GND
Pin 6 Y2:
Pin 7 GND: GND
Pin 8 Y3: 108 (Pin 7)
Pin 9 B3: Bridged 10 -> Dip3
Pin 10 A3: Bridged 9 -> Dip3
Pin 11 Y4: PRG1 (Pin 1)
Pin 12 B4: Bridged 13
Pin 13 A4: Bridged 12
Pin 14 Vcc: +5V
lidnariq wrote:... the DIP switches ...
Dip 1: 108 (Pin 28) - when closed - connects to 74HC08 (Pins 12+13)
Dip 2: PRG1 + PRG2 (Pins 27) - when closed - connects to same PRG1+PRG2 (Pins 27)
Dip 3: 108 (Pin 12) - when closed - connects to 74HC08 (Pins 9+10)
Dip 4: 108 (Pin 13) - when closed - connects to CHA (Pin 27)
lidnariq wrote:... the 127 ...
Custom 1 (127):
Pin 1: CPU (Pin 40)
Pin 2: NC
Pin 3: PRG2 A7 (Pin 3) and PRG1 (Pin 3)
Pin 4: PRG2 A6 (Pin 4) and PRG1 (Pin 4)
Pin 5: PRG2 A5 (Pin 5) and PRG1 (Pin 5)
Pin 6: PRG2 A4 (Pin 6) and PRG1 (Pin 6)
Pin 7: PRG2 A3 (Pin 7) and PRG1 (Pin 7)
Pin 8: PRG2 A2 (Pin 8) and PRG1 (Pin 8)
Pin 9: PRG2 A1 (Pin 9) and PRG1 (Pin 9)
Pin 10: PRG2 A0 (Pin 10) and PRG1 (Pin 10)
Pin 11: PRG2 D0 (Pin 11) and PRG1 (Pin 11)
Pin 12: PRG2 D1 (Pin 12) and PRG1 (Pin 12)
Pin 13: PRG2 D2 (Pin 13) and PRG1 (Pin 13)
Pin 14: GND
Pin 15: PRG2 D3 (Pin 15) and PRG1 (Pin 15)
Pin 16: PRG2 D4 (Pin 16) and PRG1 (Pin 16)
Pin 17: PRG2 D5 (Pin 17) and PRG1 (Pin 17)
Pin 18: PRG2 D6 (Pin 18) and PRG1 (Pin 18)
Pin 19: PRG2 D7 (Pin 19) and PRG1 (Pin 19)
Pin 20 74LS139 /1Y1 (Pin 5)
Pin 21: PRG2 A10 (Pin 21) and PRG1 (Pin 21)
Pin 22: 74LS139 /2Enable (Pin 15)
Pin 23: NC?
Pin 24: PRG2 A9 (Pin 24) and PRG1 (Pin 24)
Pin 25: PRG2 A8 (Pin 25) and PRG1 (Pin 25)
Pin 26: NC?
Pin 27: NC?
Pin 28: +5V
lidnariq wrote:... and ... what are those two diodes (1S1588) doing?
PPU A10 (Pin 28)
PPU A9 (Pin 29) -> D1 -> (CHR-ROM) Pin 28
PPU A8 (Pin 30) -> D2 -> (and also CHR-ROM Pin 25) -> 1A (CHR-ROM) Pin 28