Microcomputer architecture and interfacing eeng383 spring. Ttlcmos interface with opencollector output and pullup resistor. When 5v supply is given to ttl and cmos ics, logic levels of ttl and cmos are different. This means that an rs232 signal can generally travel longer physical distances than their ttl counterparts, while still providing a reliable data transmission. This book is about how peripheral devices that is printers, keyboards, monitors, mice, modems, etc. If yours does that, the signal must exceed 4 v to be reliably picked up as high. A3 announcement a3 is up on the webpage and available for handout. The cmos driver must have a strong enough pull down to sink iil when the input to the ttl gate is low 0. This page covers ttl to cmos ic interfacing and cmos to ttl ic interfacing. A typical logic fet is the 2n7000 low current 100ma and.
Ttl configurations active pullup, wired and, totem pole, open collector. When the select input is a low logic state, each circuit translates signals from one cmos level to another. Ls ttl data formerly titled fast and ls ttl data dl121d rev. In some cases, it is not poserble to plug the output of one circuit directly to the input of the other. Zion fanout the fanout of a logic gate is the number of inputs that the gate can drive without exceeding its worstcase loading specifications.
Some parts use 20% and 80% of vdd for the guaranteed levels. Microcontroller cookbook, mike james, 2001, computers, 192 pages. Modes of the msp430 0 0 0 0 250ua 0 0 0 1 35 ua 1 1 0 1 1 ua 1 1 1 1. When interfacing 5 v cmos logic to ttl, a simple direct connection can be used. I think this is pretty good so there will be no curve. The problem arises only when the output of the cmos gate needs to lower the input of the ttl gate towards logic 0, and in the process, it needs to drain a large input current from the ttl gate. The output of a ttl device sinks current when it is low and sources current when it. Request pdf ttl logic and cmosttl interface this chapter starts with transistortransistorlogic ttl, explains the circuit operation of a ttl inverter, ttl nand and nor gates, their logic. Voh minimum output voltage level a ttl device will provide for a high signal. The advantage you get is that they draw zero gate current. What are the basic differences between cmos and ttl.
This application note provides information on how to interface a ds7 realtime clock rtc to a microcontroller and provides some example code for accessing the part. Vol maximum output voltage level a device will provide for a low signal. Io interface for ttl magnetic stripe readers, technical. Transistortransistorlogic topics ttl2 supplementary material to accompany digital design principles and practices, fourth edition, by john f. For further assistance, please contact your local on semiconductor representative. The adapter plugs into a pc comport, and appears like a serial interface to the user. Cmos circuits do not draw as much power as ttl circuits while at rest. Ttl input or output lead is defined to be positive if the. It also mentions how to interface led and lamps with ttl or cmos ic. Applied pc interfacing, graphics and interrupts, william buchanan, 1996, computers, 383 pages.
Due to longer rise and fall times, the transmission of digital signals becomes. Lower current draw requires less power supply distribution, therefore causing a simpler and cheaper design. On the other hand, ttl outputs have somewhat lower dynamic power dissipation, since the voltage swing between ttl high and low levels is smaller. This is used to interface 12v inputs to a computer. Ttl device i out r l i l t computer engineering technology g. Figure1 depicts ttl to cmos interfacing and cmos to ttl interfacing circuits.
Here you can download the free lecture notes of microprocessor and interfacing pdf notes mpi notes pdf materials with multiple file links to download. The sensor is capable of capturing a maximum resolution of 2048x1536, a minimum resolution of 2x2, and all resolutions in between. This timing diagram shows both a ttl bottom and rs232 signal sending 0b01010101. As on semiconductor has exited the fast ttl business, all fast data sheets have been removed from this publication. The following figures demonstrate how to interface a ttl signal to a cmos circuit and a cmos circuit to a ttl input. A word of caution, however, is when going the other direction and interfacing from a 5 v to a 3. Vih minimum input voltage level to be considered a high. Some ttl structures have fanouts of at least 20 for both logic levels. Kabtronics unpackingparts list transistor wall clock kit page 4.
What are the basic differences between cmos and ttl signals. Within each family, several subfamilies of logic types are available, with different rating for speed, power consumption, temperature range, voltage level and current level. But for the question about inverted ttl i think maybe a schematic from this converter can help to get the answer about the inverted ttl. If, for instance, we wished to use a singlepole, singlethrow spst switch as the input device for a ttl logic gate, what is the best way to connect such a device to a ttl input. Sep 22, 2016 interfacing cmos logic circuits can interface with other logic families, such as ttl, oerational amplifiers, and comparators. Note that the output current capability of the 4000b74c series of cmos logic gates is insufficient for them to drive ttl.
The first possible type of cmos to ttl interface is the one where both ics are operated from a common supply. Design and build microprocessorbased data acquisition and control systems. If either input a or input b is high logic 1, true, the respective mos transistor acts as a very low resistance between the output and the negative supply, forcing the output to be low logic 0, false. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Interfacing is a structural material placed between fabric layers in areas where more stability, body and support are needed beyond the fabric thicknesses themselves. Cd4504b hex voltage levelshifter consists of six circuits which shift input signals from the v cc logic level to the v dd logic level. In the following drawing, the 4041 could be omitted if the 4011 was supplied with 5v. Aug 15, 2007 the 74hc family is a cmos family, not a ttl one. To shift ttl signals to cmos logic levels, the select input is at the v cc high logic state. A digital designer selects a default logic family to use in a system, based on general requirements of speed, power, cost, and so on. There is also the 74hct family, which is compatible with ttl. Interfacing 101 page 1 you dont see interfacing in a finished garment, but you can tell if there isnt any. Ttl logic and cmosttl interface request pdf researchgate. So, you may see where the problem lies in interfacing these two signals.
If you are using transistors to interface to the outside world you may find fets. Microcontroller basics pdf slides 46p this book covers the following topics. By rstoring one jumper, the adapter can also be used to connect to a rs422 4wire interface or an rs485 2wire interface. Here, i am providing you best notes on microprocessor and interfacing unit wise and to the point 46146 46147 46148 46149 46150. It is ideal for use in pc interfacing, microcontroller based projects, robotics, or for experimental and educational purposes. We have read in earlier sections that the ttl family has a recommended supply voltage of 5 v, whereas the cmos family devices can operate over a wide supply voltage range of 3a18 v. The figures also show how to interface the two circuits if the voltage levels are incompatible. Interfacing a cmos sensor to the tms320dm642 using raw. When we interface different types of ics, it is necessary to check whether the driving ic is capable of meeting the current and voltage requirements of the load ic or not. You will save parts and get rid of the transistor saturation turn off delay and the annoying inversion. The ttl low sink current ioj is the limiting factor when interfacing to mul tiple ttl inputs. This is an nor gate implemented using transistortransistor logic. Microcontroller interfacing circuits pdf 44p download book.
However, using a symmetrical pair of transistors npn and pnp to give a near railtorail swing in a manner analogous to a cmos output was just not technologically feasible when ttl evolved. Interfacing between ecl lvecl pecl lvpecl to ttl lvttl cmos lvcmos ttl lvttl cmos lvcmos to pecl lvpecl translators when going from ecl lvecl pecl lvpecl environment to ttl cmos or lvttl lvcmos and vise versa, signal integrity and duty cycle distortion can play an important role in the success of a design. Thus, for example, you can drive any ttl input from any ttl output, but a logic gate from the low power ls subfamily may only be able to drive one gate from a higherspeed family. Just remember that ttl input will draw a couple of ma so you need to use a smaller resistor as the top resistor than the 12v. I want to interface my digital lines on my national instruments daq board to my cmos circuit. The rs232 to ttl modules have two main ports the ttl and rs232 connection as described below. Laboratory study and evaluation of microcomputer system. A ttl output can drive up to 10 standard ttl inputs or up to 40.
One reason why ttl is not designed to have a 5v logic high a ttl circuit is able to swing its output fast because it uses two transistors, one to pull it up and the other to pull it down. Usb ttl interface module introduction the usb ttl interface module for brevity, module hereafter can be used to add usb connectivity to any microcontroller or other device that is capable of standard serial communication. Microprocessor and interfacing notes pdf mpi pdf notes book starts with the topics vector interrupt table, timing diagram, interrupt structure of 8086. Rhydo technologies p ltd, golden plaza building, chitoor road, cochin, kerala, india pin. The maximum current that an input requires to pull it low. Ntype metaloxidesemiconductor logic uses ntype mosfets metaloxidesemiconductor fieldeffect transistors to implement logic gates and other digital circuits. As an example, here is a nor gate implemented in schematic nmos. User interfaces in computing tim capes march 7, 2011. Since current flows out of a ttl input in the low state, i il max has a negative value. Request pdf ttl logic and cmosttl interface this chapter starts with transistortransistorlogic ttl, explains the circuit operation of a ttl inverter, ttl. Interfacing the ds7 with an 8051compatible microcontroller mar 29, 2001 abstract.
Fig1 the schematic of the converter but this is only used if i use the computer to communicate with the meter. Fanout must be examined for both possible output states. You may wonder why the nand gate is so popular in the ttl logic. Interfacing ttl and cmos circuits national instruments. By using the 7414 hex schmitt trigger, you get hysteresis of the input. Transistortransistor logic ttl cmos logic ttl and cmos logic family is most widely used ic technologies. This inversion layer, called the nchannel, can conduct electrons between ntype source and drain terminals.
Never confuse the 74hc or 74hct cmos families with other families such as 74, 74s, 74l, 74ls and 74f ttl families. Most are concerned with interfacing tofrom ttl logic. Required pic 18f26k22 technical documents available as free pdf required iclicker2 course objectives. These nmos transistors operate by creating an inversion layer in a ptype transistor body.
Cd4504b cmos hex voltagelevel shifter for ttltocmos or. Here is a small collection of interface circuits for your own designs. Apr 21, 2017 this especially applies to logic gates fabricated using different technologies, i. Standard ttl characteristics speed, power dissipation, fanin, fanout, current and voltage parameters, noise margin, operating temperature etc. The reason is because the cmos can be supplied also with 5v like the ttl. However, the designer may select devices from other families in some cases because of availability or other special requirements. You can do so with our analogtodigital converters tutorial. Click on the inputs on the bottom to toggle their state. Business innovation centre, innova park, mollison avenue, enfield, middlesex, en3 7xu tel. Interfacing a cmos sensor to the tms320dm642 using raw capture mode 5 2. Midterms out midterms results are in the average was above 72 percent. You will explore areas of electronics integral to a wide range of modern technologies using an. Ttl outputs driving cmos inputs, and cmos out puts driving ttl.
Vil maximum input voltage level to still be considered a low. However, most cmos logic circuits in use today are compatible with ttl and lvttl levels which are the dominant 5 v and 3. Interfacing cmos to ttl with different voltages is as easy as with same voltages. When a cmos gate drives a ttl gate, the high logic output of the cmos gate does not create an issue for the input circuitry of the ttl gate. Microprocessor and interfacing pdf notes mpi notes pdf. So, a 4041 buffer can be powered with 5v to do the interface. Interfacing to mm74hc highspeed cmos logic on semiconductor.
Model 4201 however has an additional pp3 connector and onboard 5v regulator. Ttl to cmos interfacing using pullup resistor figure 2. Microcontroller components, a typical microcontroller application, motorola 68hc12 microcontroller, 68hc12 programming model, 68hc12 data types, auto prepost decrementincrement, indexed addressing, 68hc12 move instructions, hc12 logic instructions, multiply and. According to the internal ttl and lsttl ouput stage configuration, the resistor will pullup the output level up to vcc, similar to an open collector output. For example the table below reveals that the output current capability of ttl ics is much higher than the input current values of cmos ics. A voltage transfer curve is a graph of the input voltage to a gate versus its output voltage.