5V na 3.3V bus translation

[ majstorovic @ 31.08.2011. 13:09 ] @

Osnovna ideja je da se spoji MC68000 na cyclone II, e sad u tom citavom procesu potrebno je 5V I/O sa mc68000 dovesti na 3.3V LVTTL koji prihvata cyclone II. Ono sto je ovde problem je da MC68000 ne prihvata 3V TTL neke verzije prihvataju ali ova sa kojom radim ne. Da ne bi prepisivao sta se sve desava evo posta na mom jadnom engleskom koji sam postavio na jedan od foruma.

There is something wrong with quickswich devices. As I know MC68000 cant
support 3.3V (some versions can but mine just cant). When i use quickswich
any type i only get 5V to 3.3V translation and no vice versa. I need to use
dual voltage level translator with auto sensing. Only parts that I can
found with this is txs0108e even sn74lvc8t245 have direction control.
For last two days I m reading about Pericom articles and those articles are
just like IDT have for quickswich part. Devices are working from higher to
lower and I m thinking that I just cant use those devices. For some devices
who work with 5V can drive lower voltage levels that is ok but on my
situation is not. For example PI5CX and PI3CX series are only related to 5V
to 3.3V translation no bidirectional and then i need to use bus enable
input like on most devices. From A to B bus or from B to A bus, that is not
practical. Also some Pericom devices PI74LVC4245 who have two voltage on
each bus side but no auto sensing again I need to set direction sides. I
just dont know, as much i m reading only thing is txs0108e that I m using
on design right now. Also using Pericom or IDT devices we can use pull up
resistor connected to higher power source. I just dont know....

[ ZAS011 @ 31.08.2011. 13:30 ] @

http://delphys.net/d.holmes/hardware/levelshift.html

[ milanmeh @ 31.08.2011. 14:45 ] @

Koju magistralu treba da prevodis? Ako je magistrala sa jednosmernim linijama (kao SPI na primer), onda je 74LVC4245 OK resenje, ali nije bas ekonomicno ako imas mali broj linija (za SPI magistralu ti treba dva komada, jedan za MISO a drugi za MOSI, SCK i RESET). Ukoliko imas dvosmerne linije (i jos ako ih ima malo - I2C) bolje je ici na shiftovanje sa N kanalnim mosfetima.

Prostudiraj ovaj applicatio note od Philipsa: PDF. Sadrzi slican tutorijal kao sto je ZAS011 postovo ali sa nekim naprednijim cakama.

[ majstorovic @ 31.08.2011. 20:41 ] @

Ni jedan primjer koji sam nasao na netu meni ne odgovara sem ovoga txs0108e jer je on bidirekcionalni i ima ato sensing sto ce reci da u bilo kom momentu on automatski omogucava komunikaciju A i B busa odnosno B prema A. Ja vec mjesecima proucavam ovo i kompletan dizajn sam uradio vec sa txs0108 medjutim dvoumim se jer treba da ih iskoristim 8. A postoji mogucnost da se koriste neki proizvodi Pericom-a koji imaju 32 bita gdje bi mi dovoljna bila samo 2 medjutim pitanje je da li bi ja to uspio da iskombinujem. Bilo kako bilo radicu 2 prototipa pa cemo da vidimo. U svakom slucaju hvala.