5V FCT TO Cyclone II

M

majsta

Guest
Hi there, i just fount this page and i hope that you can help me. Here i
what i need to do. I want to interface MC68000 to cyclone II. As yo
allready know MC68000 is 5V system and i need to convert that signals t
3.3V so i can use it in cyclone. I was working with txs0108e and now i kno
that 5V<=>3.3V are done in bidirectional mode but i dont know what happene
to FCT to LVTTL conversion. Can it be done on this way or i need to us
some external FCT to TTL converters. Or i need to use something lik
quickswich like QS3861. Can anyone help?



---------------------------------------
Posted through http://www.FPGARelated.com
 
Yes in my first design i used quickswich devices but then i decide to go t
the newer devices like txs0108e. This is octal bi-directional bus wit
voltage level translation. And now i dont know is this design ok becus
like you write in previus post best metod is to use quickswich. What do yo
think about txs0108e in this design. Also i would not use cyclone just fo
memory, i want to use mc68000 core with sdram controler to replace mc6800
on the board.

---------------------------------------
Posted through http://www.FPGARelated.com
 
On Aug 15, 5:25 pm, "majsta" <imajstorovic@n_o_s_p_a_m.yahoo.com>
wrote:
Hi there, i just fount this page and i hope that you can help me. Here is
what i need to do. I want to interface MC68000 to cyclone II. As you
allready know MC68000 is 5V system and i need to convert that signals to
3.3V so i can use it in cyclone. I was working with txs0108e and now i know
that 5V<=>3.3V are done in bidirectional mode but i dont know what happened
to FCT to LVTTL conversion. Can it be done on this way or i need to use
some external FCT to TTL converters. Or i need to use something like
quickswich like QS3861. Can anyone help?

---------------------------------------        
Posted throughhttp://www.FPGARelated.com
Click to expand...
I am assuming that you are attaching the FPGA as a memory-mapped
device, which means that most of the signals will be unidirectional.
For these, I would suggest a simple buffer with a wide input range. I
have used the SN74LVC2G34 buffers where I need to drive a 3.3V input
on an FPGA with a TTL device, and they have worked very well. Just
power the buffer with the Vio of your FPGA, since the inputs are
tolerant up to 5.5V regardless of Vcc. You can get devices with the
same specifications in hex and octal variants.

For the bi-directional bus, I do suggest the IDT quickswitch parts.
They are are cheap, have extremely small latencies, and are fairly
simple to use. The only caveat is that to use them as voltage
translators, you do have to pay attention to the A and B side (since
they are FET based, and have an intrinsic diode), and note that you
have to supply them with a Vcc no greater than 4.2V to ensure the
output never exceeds 3.3V. However, the current demand is very small,
and most people get away with just putting a small signal diode
between the supply and the part's Vcc input. Just make sure the diode
has a Vf greater than 0.8V.
 
"majsta" <imajstorovic@n_o_s_p_a_m.yahoo.com> wrote in message
news:68-dnacDFLV-AdTTnZ2dnUVZ_tqdnZ2d@giganews.com...
Hi there, i just fount this page and i hope that you can help me. Here is
what i need to do. I want to interface MC68000 to cyclone II. As you
allready know MC68000 is 5V system and i need to convert that signals to
3.3V so i can use it in cyclone. I was working with txs0108e and now i
know
that 5V<=>3.3V are done in bidirectional mode but i dont know what
happened
to FCT to LVTTL conversion. Can it be done on this way or i need to use
some external FCT to TTL converters. Or i need to use something like
quickswich like QS3861. Can anyone help?
Click to expand...
I would offer You to use simple and trivial SN74LVC8T245. Thats also 8bit
translator with two voltages.
 
scrts <hidden@email.com> wrote:

"majsta" <imajstorovic@n_o_s_p_a_m.yahoo.com> wrote in message
news:68-dnacDFLV-AdTTnZ2dnUVZ_tqdnZ2d@giganews.com...
Hi there, i just fount this page and i hope that you can help me. Here is
what i need to do. I want to interface MC68000 to cyclone II. As you
allready know MC68000 is 5V system and i need to convert that signals to
3.3V so i can use it in cyclone. I was working with txs0108e and now i
know
that 5V<=>3.3V are done in bidirectional mode but i dont know what
happened
to FCT to LVTTL conversion. Can it be done on this way or i need to use
some external FCT to TTL converters. Or i need to use something like
quickswich like QS3861. Can anyone help?

I would offer You to use simple and trivial SN74LVC8T245. Thats also 8bit
translator with two voltages.
Click to expand...
Why not stay with the switches? That saves you from switching direction in
the drivers.

Bye

--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
 
On 08/16/2011 09:20 AM, majsta wrote:
Yes in my first design i used quickswich devices but then i decide to go to
the newer devices like txs0108e. This is octal bi-directional bus with
voltage level translation. And now i dont know is this design ok becuse
like you write in previus post best metod is to use quickswich. What do you
think about txs0108e in this design. Also i would not use cyclone just for
memory, i want to use mc68000 core with sdram controler to replace mc68000
on the board.
Click to expand...
Make sure when you use a converter like that that Vih on the 5V side is
low enough for TTL. From the looks of it, that is *not* true for
TXS0108E when Vccb = 5V.

The reason quickswitches work for 5 V TTL <-> 3.3 V CMOS is because
3.3 V leverages the assymetry in 5 V TTL voltages; active buffers are
usually better for CMOS-to-CMOS conversion...

-hpa
 
Ok but i ll stay with this design, I dont know I just cant change desig
now, and many peolpe told me that it can work with txs0108e. Thank you fo
your time. Also I want to ask is there are any examples of Mc68000 an
sdram controller in VHDL combinations.

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

---------------------------------------
Posted through http://www.FPGARelated.com
 
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