I would like to integrate an 8051 microcontroller to a spartan 3 development
board. For input port I know I need to add a series resistor. However for
the output ports, I have read posts and app notes about using the
quickswitch product. The only problem is the package that they come in. I
have been wire wrapping most of my pins thus far and have not found any
level shifting solutions that comes in a DIP package (that can be wire
wrapped). So here is my question: instead of using the level shifter, can
I just directly connect my Spartan 3 output port to an input port on my 8051
and have a pull-up resistor to 5V on the same net? My idea is that for low
outputs I would just output a low logic level, but for a high output, I
would create the VHDL code to output a high impedance (Z)... Does anyone
think this will work, or am I just crazy?
Thanks for any suggestions!
Larry
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Spartan 3 output voltage level
Started by ●November 21, 2004
Reply by ●November 21, 20042004-11-21
Just use the series resistor to limit the 8051->S3 high-level current. In the S3->8051 direction, you don't need anything since LVTTL (3.3V supply) has exactly the same logic thresholds as TTL (5V supply). If you do need any pullups then connect them to 3.3V -- not 5V. Bob "Lawrence Kiss" <lkiss80@hotmail.com> wrote in message news:41a15113$1_1@127.0.0.1...> I would like to integrate an 8051 microcontroller to a spartan 3development> board. For input port I know I need to add a series resistor. Howeverfor> the output ports, I have read posts and app notes about using the > quickswitch product. The only problem is the package that they come in.I> have been wire wrapping most of my pins thus far and have not found any > level shifting solutions that comes in a DIP package (that can be wire > wrapped). So here is my question: instead of using the level shifter,can> I just directly connect my Spartan 3 output port to an input port on my8051> and have a pull-up resistor to 5V on the same net? My idea is that forlow> outputs I would just output a low logic level, but for a high output, I > would create the VHDL code to output a high impedance (Z)... Does anyone > think this will work, or am I just crazy? > > Thanks for any suggestions! > > Larry > > > > Posted Via Usenet.com Premium Usenet Newsgroup Services > ---------------------------------------------------------- > ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** > ---------------------------------------------------------- > http://www.usenet.com
Reply by ●November 22, 20042004-11-22
"Lawrence Kiss" <lkiss80@hotmail.com> schrieb im Newsbeitrag news:41a15113$1_1@127.0.0.1...> I would like to integrate an 8051 microcontroller to a spartan 3development> board. For input port I know I need to add a series resistor. Howeverfor> the output ports, I have read posts and app notes about using the > quickswitch product. The only problem is the package that they come in.I> have been wire wrapping most of my pins thus far and have not found any > level shifting solutions that comes in a DIP package (that can be wire > wrapped). So here is my question: instead of using the level shifter,can> I just directly connect my Spartan 3 output port to an input port on my8051> and have a pull-up resistor to 5V on the same net? My idea is that forlow> outputs I would just output a low logic level, but for a high output, I > would create the VHDL code to output a high impedance (Z)... Does anyone > think this will work, or am I just crazy? > > Thanks for any suggestions! > > Larry > > > > Posted Via Usenet.com Premium Usenet Newsgroup Services > ---------------------------------------------------------- > ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** > ---------------------------------------------------------- > http://www.usenet.comWhy not running the 8051 at 3V3 ??? There are lot of 3V3 compatible 8051 MCU�s / CPU�s .... with best regards, Peter Seng ############################# SENG digitale Systeme GmbH Im Bruckwasen 35 D 73037 Goeppingen Germany tel +7161-75245 fax +7161-72965 eMail p.seng@seng.de net http://www.seng.de #############################
Reply by ●November 22, 20042004-11-22
I am taking an embedded systems course. We had to buy a parts kit that was available only from the prof. The semester is coming to a close within 2 weeks, and everyone is trying to finish their final (open ended) projects. No time to convert everything that I have been doing all semester to 3.3. Thanks for the suggestion though. "Peter Seng" <NOSPAM@seng.de> wrote:> >"Lawrence Kiss" <lkiss80@hotmail.com> schrieb im Newsbeitrag >news:41a15113$1_1@127.0.0.1... >> I would like to integrate an 8051 microcontroller to a spartan 3 >development >> board. For input port I know I need to add a series resistor. However >for >> the output ports, I have read posts and app notes about using the >> quickswitch product. The only problem is the package that they come in. >I >> have been wire wrapping most of my pins thus far and have not found any >> level shifting solutions that comes in a DIP package (that can be wire >> wrapped). So here is my question: instead of using the level shifter, >can >> I just directly connect my Spartan 3 output port to an input port on my >8051 >> and have a pull-up resistor to 5V on the same net? My idea is that for >low >> outputs I would just output a low logic level, but for a high output,I>> would create the VHDL code to output a high impedance (Z)... Does anyone >> think this will work, or am I just crazy? >> >> Thanks for any suggestions! >> >> Larry >> >> >> >> Posted Via Usenet.com Premium Usenet Newsgroup Services >> ---------------------------------------------------------- >> ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** >> ---------------------------------------------------------- >> http://www.usenet.com > > > >Why not running the 8051 at 3V3 ??? >There are lot of 3V3 compatible 8051 MCU�s / CPU�s .... > > >with best regards, > >Peter Seng > > >############################# >SENG digitale Systeme GmbH >Im Bruckwasen 35 >D 73037 Goeppingen >Germany >tel +7161-75245 >fax +7161-72965 >eMail p.seng@seng.de >net http://www.seng.de >############################# > >----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =---
Reply by ●November 22, 20042004-11-22
You are unlikely to get a bus switch in anything other that surface mount. We use this technique on our Broaddown2 product and it works well. If you don't have to operate at high speed then you can consider using a series resistor but only if the Vcco of the Spartan-3 is guaranteed less than 3.3V. The input of the S3 should not go above 4.05V( from memory) and the protection diodes will present a rise over Vcco of about 0.7V. Going the other way from S3 to 8051 check the input voltage levels. they may be CMOS levels and if so might expect 4.0V (at worst) for a "high" input. You will not achieve 4.0V from S3 and pullup may be needed. The S3 will probably draw current from a pullup if connected to 5V so you will need to look at the ratio of pullup to series resistor values. If you are looking at small number of lines, at lowish speed, then you may be able to use something like back to back RS232 drivers to do a level shift. Or you could also use discrete mosfets. Bus switches are essentially mosfets. Slightly rusty on this area but I think we are talking n-channel with gate connected to Vcc. Cut off voltage depends on mosfet type. John Adair Enterpoint Ltd. - Home of Broaddown2. The Ultimate Spartan3 Development Board. http://www.enterpoint.co.uk "Lawrence Kiss" <lkiss80@hotmail.com> wrote in message news:41a15113$1_1@127.0.0.1...> I would like to integrate an 8051 microcontroller to a spartan 3development> board. For input port I know I need to add a series resistor. Howeverfor> the output ports, I have read posts and app notes about using the > quickswitch product. The only problem is the package that they come in.I> have been wire wrapping most of my pins thus far and have not found any > level shifting solutions that comes in a DIP package (that can be wire > wrapped). So here is my question: instead of using the level shifter,can> I just directly connect my Spartan 3 output port to an input port on my8051> and have a pull-up resistor to 5V on the same net? My idea is that forlow> outputs I would just output a low logic level, but for a high output, I > would create the VHDL code to output a high impedance (Z)... Does anyone > think this will work, or am I just crazy? > > Thanks for any suggestions! > > Larry > > > > Posted Via Usenet.com Premium Usenet Newsgroup Services > ---------------------------------------------------------- > ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** > ---------------------------------------------------------- > http://www.usenet.com
Reply by ●November 22, 20042004-11-22
Thanks for the reply Peter. My 8051 specifies a minimum high logiv level at .7*VCC = 3.5V. What is the gaurentee that the Spartan 3 will ever output a 3.3V signal? I would think that I need to pull up to VCC=5V not 3.3V. Larry "Peter Seng" <NOSPAM@seng.de> wrote:> >"Lawrence Kiss" <lkiss80@hotmail.com> schrieb im Newsbeitrag >news:41a15113$1_1@127.0.0.1... >> I would like to integrate an 8051 microcontroller to a spartan 3 >development >> board. For input port I know I need to add a series resistor. However >for >> the output ports, I have read posts and app notes about using the >> quickswitch product. The only problem is the package that they come in. >I >> have been wire wrapping most of my pins thus far and have not found any >> level shifting solutions that comes in a DIP package (that can be wire >> wrapped). So here is my question: instead of using the level shifter, >can >> I just directly connect my Spartan 3 output port to an input port on my >8051 >> and have a pull-up resistor to 5V on the same net? My idea is that for >low >> outputs I would just output a low logic level, but for a high output,I>> would create the VHDL code to output a high impedance (Z)... Does anyone >> think this will work, or am I just crazy? >> >> Thanks for any suggestions! >> >> Larry >> >> >> >> Posted Via Usenet.com Premium Usenet Newsgroup Services >> ---------------------------------------------------------- >> ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** >> ---------------------------------------------------------- >> http://www.usenet.com > > > >Why not running the 8051 at 3V3 ??? >There are lot of 3V3 compatible 8051 MCU�s / CPU�s .... > > >with best regards, > >Peter Seng > > >############################# >SENG digitale Systeme GmbH >Im Bruckwasen 35 >D 73037 Goeppingen >Germany >tel +7161-75245 >fax +7161-72965 >eMail p.seng@seng.de >net http://www.seng.de >############################# > >----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =---
Reply by ●November 22, 20042004-11-22
Lawrence Kiss wrote:> My 8051 specifies a minimum high logiv level at .7*VCC = 3.5V. What is the > gaurentee that the Spartan 3 will ever output a 3.3V signal? I would think > that I need to pull up to VCC=5V not 3.3V.Many processors have more strict Vih for clock and reset inputs, which can easily be 0.7Vcc, though that would be unusual for other inputs. Otherwise, if Vih-Vil is not too large you can use a diode or two, along with a pull up resistor, to shift the voltage up as appropriate. If there are protection diodes on the outputs of the Spartan, you won't be able to get them much higher than the output supply voltage. -- glen
Reply by ●November 22, 20042004-11-22
"Bob" <nimby1_notspamm_@earthlink.net> wrote in message news:<Gwcod.8180$pK6.1111@newsread2.news.atl.earthlink.net>...> Just use the series resistor to limit the 8051->S3 high-level current. > > In the S3->8051 direction, you don't need anything since LVTTL (3.3V supply) > has exactly the same logic thresholds as TTL (5V supply).That should work with most logic familiers - if he has to talk to 5v devices that really need a higher input voltage, he should be able to use widely available 74-whatever-xx DIP package buffers or inverters in a 3.3v volt-compatible logic family as stand-in level translators. Of course, why not simply move the "8051" into the FPGA?? Chris
Reply by ●November 22, 20042004-11-22
"Chris Stratton" <cs_posting@hotmail.com> wrote in message news:ae2ff5ca.0411221453.1b082f07@posting.google.com...> "Bob" <nimby1_notspamm_@earthlink.net> wrote in messagenews:<Gwcod.8180$pK6.1111@newsread2.news.atl.earthlink.net>...> > Just use the series resistor to limit the 8051->S3 high-level current. > > > > In the S3->8051 direction, you don't need anything since LVTTL (3.3Vsupply)> > has exactly the same logic thresholds as TTL (5V supply). > > That should work with most logic familiers - if he has to talk to 5v > devices that really need a higher input voltage, he should be able to > use widely available 74-whatever-xx DIP package buffers or inverters > in a 3.3v volt-compatible logic family as stand-in level translators. > > Of course, why not simply move the "8051" into the FPGA?? > > ChrisIt looks like his 8051 is not (LV)TTL compatible. He will need some sort of translation. You are right, though. If I were he, I would stuff that uP into the FPGA. I looked at opencores.org http://www.opencores.org/browse.cgi/by_category but didn't see any 8051's. Maybe he can some other processor core. Bob
Reply by ●November 23, 20042004-11-23
Bob <nimby1_notspamm_@earthlink.net> wrote: : It looks like his 8051 is not (LV)TTL compatible. He will need some sort of : translation. : You are right, though. If I were he, I would stuff that uP into the FPGA. I : looked at opencores.org To interface 3.3V CMOS (which is also real TLL levels) to 5 Volt CMOS, use some (X)CT Logic, like 74ACT Bye -- Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
