LVTTL is increasingly becoming popular these days, because of the nominal HIGH voltages, and hence lesser power consumption. LVTTL stands for Low Voltage Transistor- Transistor Logic. But since attaining exact +5 volts and 0 volt is practically not possible every time, various IC manufactures define TTL logic level range differently, but the usual accepted range for a HIGH is within +3.5 ~ +5.0 volts, and the range for a LOW is 0 ~ +0.8 volts. In TTL Logic, a HIGH (or 1) is +5 volts, whereas a LOW (or 0) is 0 volts. A major drawback of the TTL logic is that most of the devices working on the TTL Logic consume a lot of current, even individual gates may draw up to 3-4 mA. TTL is mostly used in ICs and gates, like 74xx logic gates. These days TTL is the most widely used logic. TTL stands for Transistor- Transistor Logic. Various logic levels have been standardized, out of which the most popular ones are: 1. Btw, have you heard of TTL? Sounds familiar, but what is TTL? Lets read on!īy ‘Logic Level’ one means the range of voltage over which a high bit (1) and a low bit (0) is accepted in a particular IC, gate, etc. The other pins are not of much use to us, for now. And this is what we will be doing here and hence forth in upcoming posts. NOTE: Another important thing to note is that the simplest way to in which a microcontroller can communicate to a PC is through RxD, TxD, and Ground Pins. Now what does this mean? In simple words, it means that serial communication through the DB-25 connector could take place through two channels simultaneously (thanks again, Thomas!). Yes, it looks exactly like (in fact it is) the parallel (printer) port you would find in even older computers! Even though it is called the parallel port, data transfer takes place using the serial protocol (thanks Thomas for clarification).Īs we can see, most of the pins are similar to that of a DB9 port. If you notice, we see that in DB25 connector there are two TxD and RxD pairs of pins. The pin configuration of DB-25 port is as follows. This is the pin through which data is transmitted to the receiver.
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