I have to design and build a system capable of the following;

1) A 4-bit number is to be obtained from a 4-bit dil switch and on the press of another switch the 7-bit ASCII equivalent is to be transmitted via a simple synchronous serial comm link.
2) The comm link is to operate on ttl levels and comprises three wires: data, ground and clock.
3) A receiever is to detect when a transmission has ocured and display the hexidecimal equivalent on two 7-seg displays.

I am not totally certain of what I am being asked to do my interpretation is you enter a 4 bit binary number i.e. 0-15 in decimal, the ASCII equivalent of the number 0-15 is sent across, though any number greater then nine would be more then 7 bits. Then at the reciever end this is converted to the hex equivalent of the decimal number between 0 and 15. Could you tell me if you agree that this is what I need to do.

cheers

 

Out of curiosity, do you know the ASCII codes for numerals? Is there a code for 15?

 

Your reasoning looks ok, but it will be a pain to transmit the data serially and store it for display. I guess, however, that the receiver and the transmitter circuits will be dual to each other.