Search found 486 matches

by Ben Boldt
Mon Feb 17, 2020 9:53 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

Just a quick update, I updated the A/B/C1/C2 simulator from before with the 3 state machine / 2 counter idea from the previous diagram I shared. I don't understand how yet but it does usually get the extra scanline correct when doing the A/B/C1/C2 test. I have at least 2 A/B/C1/C2 combinations that ...
by Ben Boldt
Fri Feb 14, 2020 2:42 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

New drawing, definite progress being made understanding this thing. The work I did before without toggling PA12 within each scanline turns out is still very valid information. It is not necessary to toggle it for the info I was looking for. It takes 1 M2 cycle with PA12 high to detect entering the s...
by Ben Boldt
Thu Feb 13, 2020 4:49 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

Latest text description, untested, but now at least considering this behavior where you can use a new reload value right away. It is not narrowed down to the IRQ being ACKed enabling this ability, that is still unknown what exactly opens the doors to make that immediately writable -- I just know tha...
by Ben Boldt
Wed Feb 12, 2020 3:13 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

Scopeshots:
orig.png
after first rising edge.png
after first falling edge.png
by Ben Boldt
Wed Feb 12, 2020 12:03 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

I am simulating it more accurately now and I am seeing something interesting. It sure looks like my test is still screwed up but I thought I would share in case it triggers any ideas for you. The green channel inverts each time I start a new scanline. I am probably off by a scanline, either that or ...
by Ben Boldt
Tue Feb 11, 2020 7:50 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom AV board check
Replies: 7
Views: 260

Re: Famicom AV board check

Your schematic is usually followed by another transistor as an extra buffer. I guess I haven't really thought about that before. The extra buffer is typically inside the RF box right? What is the benefit of adding the extra buffer? My AV modded famicoms only use the 1 transistor, I am very interest...
by Ben Boldt
Tue Feb 11, 2020 7:16 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom AV board check
Replies: 7
Views: 260

Re: Famicom AV board check

The arrow is going the wrong way on your 2SA1015 transistor -- it makes it the symbol for NPN, so it isn't clear what you intended to do. The 2SA1015 is actually a PNP transistor. https://www.allaboutcircuits.com/uploads/articles/tech_PNP_3.jpg Pay extra-special attention to the pinout of the transi...
by Ben Boldt
Mon Feb 10, 2020 11:25 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom AV Mod Situation in 2019
Replies: 129
Views: 88236

Re: Famicom AV Mod Situation in 2019

Very interesting. I don't often go into that section of the forum. I don't know how the jailbars are persisting so well. It would be helpful to swap the "RF" boxes (not sure I should call them that), or see the composite video directly through the AV mod circuit, eliminating the composite-to-rgb con...
by Ben Boldt
Mon Feb 10, 2020 6:48 pm
Forum: NES Hardware and Flash Equipment
Topic: Famicom AV Mod Situation in 2019
Replies: 129
Views: 88236

Re: Famicom AV Mod Situation in 2019

I am so absent-minded lidnariq, thanks a lot for your helpful corrections as usual with the typo fix and addition in the wiki.
by Ben Boldt
Mon Feb 10, 2020 8:21 am
Forum: NES Hardware and Flash Equipment
Topic: Famicom AV Mod Situation in 2019
Replies: 129
Views: 88236

Re: Famicom AV Mod Situation in 2019

This thread has gotten pretty long, but we came up with what we thought was the best possible circuit, based very closely to the AV Famicom. I have put it into the wiki here: https://wiki.nesdev.com/w/index.php/PPU_pin_out_and_signal_description#Composite_Video_Output I am not sure if this is the be...
by Ben Boldt
Fri Feb 07, 2020 12:43 pm
Forum: NES Hardware and Flash Equipment
Topic: Broken PPUs/CPUs from China
Replies: 9
Views: 466

Re: Broken PPUs/CPUs from China

I open disputes all the time, probably 5-10% of my orders get a dispute. I have not noticed any problem yet. If you are already on the naughty list, then you may as well do more disputes, it can't really hurt at that point!
by Ben Boldt
Wed Feb 05, 2020 5:29 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

I desoldered the pin 19 of RAMBO-1 chip and it is not internally connected to GND, it is rather some kind of input pin. When tied to 5V (through 1k resistor for safety reasons), RAMBO-1 constantly drives the data bus with byte 0x05, no matter if this is read or write cycle. And when accessing 8000-...
by Ben Boldt
Wed Feb 05, 2020 4:51 pm
Forum: NES Hardware and Flash Equipment
Topic: RAMBO-1 Mapper Investigation
Replies: 94
Views: 14326

Re: RAMBO-1 Mapper Investigation

Any chance that pin 19 either exposes the CIC or IRQ state? I played with pin 19 starting in the first page of this thread. It definitely puts the chip into a different mode. It prevents writing to most registers and causes other seemingly nonsensical behaviors. It is located right next to the CIC ...
by Ben Boldt
Wed Feb 05, 2020 8:49 am
Forum: Reproduction
Topic: (SNES) Changing Chrono Trigger (J) into (U)
Replies: 16
Views: 1917

Re: (SNES) Changing Chrono Trigger (J) into (U)

Yes they are '157's! Nice catch!
by Ben Boldt
Tue Feb 04, 2020 7:00 pm
Forum: Reproduction
Topic: (SNES) Changing Chrono Trigger (J) into (U)
Replies: 16
Views: 1917

Re: (SNES) Changing Chrono Trigger (J) into (U)

Oh crap, hopefully that was a typo, I will have to double-check tomorrow. I have not run that cart yet. Thanks for noticing.