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5V FCT TO Cyclone II

Started by majsta August 15, 2011
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?

	   
					
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On Aug 15, 5:25=A0pm, "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 kn=
ow
> that 5V<=3D>3.3V are done in bidirectional mode but i dont know what happ=
ened
> 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? > > --------------------------------------- =A0 =A0 =A0 =A0 > Posted throughhttp://www.FPGARelated.com
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.
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.	   
					
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"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.
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.
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.
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 design
now, and many peolpe told me that it can work with txs0108e. Thank you for
your time. Also I want to ask is there are any examples of Mc68000 and
sdram controller in VHDL combinations.	   
					
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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 sn74lvc8t245 and new one like I write before txs0108e.
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....	   
					
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