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by exxos
Sat Jun 22, 2019 1:02 pm
Forum: HARDWARE DISCUSSIONS
Topic: Cartridge Port: Would a buffer board help with problems?
Replies: 18
Views: 249

Re: Cartridge Port: Would a buffer board help with problems?

That's about as good as things get.. But does it help ?
by exxos
Sat Jun 22, 2019 10:31 am
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

I assume as the Falcon has 2 registers for address and data, that it drives the "AS" pin on address, and doesn't for data. So the CPU must do 2 bus accesses to the RTC... and once the RTC has had the address "set" it stores it and can be accessed later in a second bus cycle. On the memory map http:/...
by exxos
Sat Jun 22, 2019 10:24 am
Forum: HARDWARE ISSUES
Topic: C-Sync on 520ST C070115 REV.2B
Replies: 4
Views: 58

Re: C-Sync on 520ST C070115 REV.2B

Can't really see have you wired it up from your image..
by exxos
Fri Jun 21, 2019 11:01 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

stephen_usher wrote:
Fri Jun 21, 2019 10:59 pm
From my reading it doesn't look at the 'R/W' line until the read/write part of the cycle and that determines whether it reads the bus or writes onto the bus.
That makes sense.. but why didn't they "XXXX" out the RW line in the timing diagram to just indicate "don't care" :shrug:
by exxos
Fri Jun 21, 2019 10:30 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

6.jpg So CS going high doesn't clear the selected address I think... So the 68000 would put the address on the databus, CS = low, DS=low, but can't figure out what RW is supposed to be doing at that point :roll: I mean the first bus cycle would select the register, then read or write data to it on ...
by exxos
Fri Jun 21, 2019 10:09 pm
Forum: HARDWARE DISCUSSIONS
Topic: Cartridge Port: Would a buffer board help with problems?
Replies: 18
Views: 249

Re: Cartridge Port: Would a buffer board help with problems?

Bad address and databus etc is the route of most of my troubles..What you see is "normal" for the ST. Its a wonder the things ever booted or worked from day 1. Like I said earlier, my diagnostic board wouldn't boot with "Finger on board", so the resistance of my fingers was enough to cause the machi...
by exxos
Fri Jun 21, 2019 9:58 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

The problem I see is, my RTC board is only wired into the databus.. There would be no way to keep CS low and do both address and data bus cycles in 1 single 68000 cycle :roll: . I think it would be simpler to wire the RTC AD pins to the 68000 address bus, and have a multiplexer chip which can switch...
by exxos
Fri Jun 21, 2019 9:45 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

Its wired for MOT timing. It says DS sets the time it drives the bus. So makes sense when AS is high, its loading the address, so we don't want it to drive data on the bus, so DS is kept low. So when AS goes high, we basically select data access, and DS sets how long we want the RTC to output data. ...
by exxos
Fri Jun 21, 2019 9:27 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

hmmm, I think "AS" on the RTC is literally address select, and data otherwise... I've been mistaking it for "AS" on the CPU which isn't "AS" on the RTC :roll: EDIT: yep. http://www.waveguide.se/?article=ds1685-rtc-on-the-motorola-bus The problem with the DS1685 is that is it not made for the Motorol...
by exxos
Fri Jun 21, 2019 9:15 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reading & write to RTC 12887 ?
Replies: 15
Views: 212

Re: Reading & write to RTC 12887 ?

I found this PDF https://www.maximintegrated.com/en/app- ... vp/id/1145

Not sure it really helps tho :roll: