TTL output

Electronics Computer Programming Q&A
Post Reply
kaola_su
Posts: 3
Joined: Mon Jul 11, 2005 1:01 am
Contact:

TTL output

Post by kaola_su » Mon Jul 11, 2005 10:37 am

How does a TTL output works? and How can i use it with an 8051 microcontroller?. Please I need this info soon, email it to [email protected]. Thank you :(

rstofer
Posts: 115
Joined: Sun May 15, 2005 1:01 am
Contact:

Re: TTL output

Post by rstofer » Mon Jul 11, 2005 12:24 pm

This info is all over Google. The output stage of a TTL device has two transistors; one to pull up and the other to pull down. The logic ahead of the drivers insures that only one transistor is conducting.<p>You shouldn't have any problem interfacint low power Shottky to the 8051. Any of the 74LSxx should work.<p>You might want to review the 74HCx series http://www.semiconductors.philips.com/a ... ATIONS.pdf

User avatar
philba
Posts: 2050
Joined: Tue Nov 30, 2004 1:01 am
Location: Seattle
Contact:

Re: TTL output

Post by philba » Mon Jul 11, 2005 1:18 pm

Rick is right - in general, use 74HTC to go to and from TTL and CMOS interfaces.<p>What is the 8051? If its an old intel part it may be NMOS (basically TTL with lower drive).<p>Also, if the 8051 is CMOS, I believe you can run it at 3.3V and not have to use interface logic. check the 8051 datasheet for input threshold - if its around 1.4V (with 3.3V supply) you should be OK.

rstofer
Posts: 115
Joined: Sun May 15, 2005 1:01 am
Contact:

Re: TTL output

Post by rstofer » Mon Jul 11, 2005 2:39 pm

The 8051 is the grandparent of all microcontrollers. There were a couple before it like the 8048 (?) but the 8051 is still in full use. There are hundreds of clones with enhanced gadgets. My personal favorite is the Philips 80C552. It has all the timers, PWM, USART, I2C, etc of the modern PIC but it has 64k of code space and 64k of data space - Harvard architecture. They aren't especially fast but they control all kinds of systems.<p>I have a wonderful Pascal compiler for the 8051 family - http://users.iafrica.com/r/ra/rainier/<p>There are wide variations in Vcc allowed but I run mine at 5V just like LSTTL. I really try to resist the 3.3V thing but with FPGAs it is getting difficult. I try to stay with the Xilinx Spartan IIE as it has 5V tolerant I/O (requires a series 100 ohm resistor).

User avatar
philba
Posts: 2050
Joined: Tue Nov 30, 2004 1:01 am
Location: Seattle
Contact:

Re: TTL output

Post by philba » Mon Jul 11, 2005 3:38 pm

I'm quite familiar with the 8051 and its incredible number of offspring. There are even DACs that have embedded 8051s. I was, obviously unclearly, asking which variant he was using. I think I have a couple of UVPROM 8051s from Intel in my junk, uh, box.

kaola_su
Posts: 3
Joined: Mon Jul 11, 2005 1:01 am
Contact:

Re: TTL output

Post by kaola_su » Tue Jul 12, 2005 11:00 am

HI!!
I need to connect a barcode reader with a TTL output to the microcontroller, but the question is, should i connect this as a parallel interface or as a serial interface (like RS232). Which are the pinouts of the ttl output?
THANK YOU :)

User avatar
philba
Posts: 2050
Joined: Tue Nov 30, 2004 1:01 am
Location: Seattle
Contact:

Re: TTL output

Post by philba » Tue Jul 12, 2005 11:38 am

OK, you need to start doing your homework before you come and ask questions like that. you give zero information on the microcontroller (which I would guess is a DS5000T from your other post) and zero information on the bar code scanner. Find and read the documents. When you ask a question here, include some relevent information. <p>Your question is like "how fast can my car go?" It's got 4 wheels and a radio.<p>I'm willing to help but not unless you put out a little effort on your part.<p>Phil

jimandy
Posts: 570
Joined: Sat Dec 04, 2004 1:01 am
Location: Birmingham AL USA
Contact:

Re: TTL output

Post by jimandy » Tue Jul 12, 2005 4:30 pm

Hang in there kaola_su. You'll get more help than you might ask for from this forum. Members struggle to answer 'how to' questions where the info needed is
1) what I am trying to do is...
2) my level of knowledge is...
3) (sometime) my language limitations...
"if it's not another it's one thing."

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests