Pokun wrote:Yes and maybe a buzzy microphone would also mess with the Zapper. I think the microphone needs a separate wire.
But only if there are games that care about both at the same time, right? The point is that on the AV Famicom there's no microphone unless the user added it... Whereas on the original Famicom someone theoretically could have held the P2 controller as a mic and the zapper at the same time.
So it's true that if a game expects the microphone, and the zapper is plugged in instead, it'll get a nonsense signal, and vice versa ... but if the right peripheral is plugged in, and no game cares about both at the same time, I can't figure out why it wouldn't be ok?
Also, I sat down and traced the picture of the PCB of the US Four Score, and found something interesting... they didn't swap the various pins on the ASIC around to achieve the changed signature... I think the signature might be controlled by pin 12... either that, or pins 13-16 are wired differently and
pin 12 routes the different signals differently.
Code: Select all
P2 Clk <- |o 1 22 | -- 5V
P2 Dat -> | 2 21 | <- 2//4
P3 Clk <- | 3 20 | -> P1 Clk
P3 Dat -> | 4 19 | <- P1 Dat
P4 Clk <- | 5 18 | -> relayed OUT
P4 Dat -> | 6 17 | <- *out?
TurboB -> | 7 16 | -> *4016d?
TurboA -> | 8 15 | <- *clk1?
C/RA -> | 9 14 | -> *4017d?
RB <- | 10 13 | <- *clk2?
Gnd -- | 11 12 | <- gnd***
* can't verify, assumed same as preceding pinout.
*** note change
(edit:) Have to admit I'm tempted to get my hands on a Four Score just so that I can see what changes if I change what pin 12 is tied to.
Pull-ups R2, R3, & R4 on the board pull "out", "clk1", and "clk2" high. Current-limiting resistors R9, R10 prevent bus conflicts (with what??) on "4016d" and "4017d". Every pin between the ASIC and one of the controller jacks has undervoltage protection diodes (nine in total: one for OUT, four for DATA and four for CLOCK). Every data pin from a controller has a pull-up resistor.
Also, in hindsight, there's no reason the Four Score needs its own 25µs RC to detect when to restart the serial stream, so I'm not entirely certain what it is
for. It's too fast to just
be the turbo button control, although they obviously could have a digital divider inside.