hi, i am trying to connect rf module with 8051. i have connected rf module using UART. i have transmitted and received the data but am not able to compare it with stored value at the receiver end. Also there is some voltage drop in the receiver output as soon as i connect the Rx pin to the reciever module. Can anyone help?? thnaks.
In the data sheet they say the output is capable of driving one TTL or one CMOS load but basically it is CMOS compatible. As the controller is TTL therotically it should be able to give the ouput of nearly 5V. But definitely it is not RS232 and i think we won't need a MAX 232 for this.
"As the controller is TTL therotically it should be able to give the ouput of nearly 5V."
Take a closer look at the datasheets for TTL logic. Why do you think TTL logic gates may accept 2.4V as a high level for the inputs, if the TTL outputs reaches nearly 5V? It's the CMOS logic that has almost full swing between GND and VCC.
Few chips in use now are TTL, so it is a term that should be avoided unless it really do mean the TTL technology. The generic term is logic-level. And there is always a need to complement "logic-level" with the full set of voltage parameters. Worst-case low and high output levels, and min required low and high input levels. Since almost everything are CMOS these days, inputs normally doesn't consume a static current - the current drive of outputs are normally only needed to charge/discharge capacitances during transitions.
You say "the datasheet". It is important that you are clear about when you are talking about the processor side, and when you are talking about the radio module side. And how about posting links to "the datasheet"?
None of this has anything to do with Keil!
We are discussing hardware issues here - and that is hard to do without a schematic diagram of the system - aka "circuit diagram"
This forum doesn't support posting images - another reason why this is not a great place for such discussions!
You might be better to go to http://www.8052.com/forum If you do, be sure to give a full & clear description of what you are trying to achieve, what you are using, what you have done so far, and what problems you are having. Give a link to this thread, and also update this thread with a link. Show your schematic. Include links to your datasheets. etc...
Few chips in use now are TTL, so it is a term that should be avoided unless it really do mean the TTL technology. nevertheless that is the term that is prevalent in datasheets for such.
anyhow 'TTL' is levels compatible with both 5V and 3V3 CMOS
Erik
When people who write datasheets are wrong, we shouldn't redefine the use as correct but instead insist on using correct definitions. Someday, the people who do write the incorrect datasheets might possibly learn that TTL is a very specific term for a specific concept involving bipolar transistors and with totem-pole outputs that can't get near the VCC rail.