| ??? 10/31/06 21:12 Read: times |
#127165 - possible Responding to: ???'s previous message |
Erik Malund said:
Does anyone know of the top of there head a 3.3VTTL through hole, preferably single or dual gate that would work here?
If you use 74HCT you get 3V3 input and 5V output with a 5V supply for both the gate and the transciever. TTL or LSTTL will work as well, if the line can handle the load. PS do you really want an AND, not an OR??? Erik Erik http://www.8052.com/forumchat/read.phtml?id=127161 This UM232 device has jumpers for 5V use as well. I want the inputs to whatever device I use to not interfear with the serial line being monitored. One concern with using a 5V device (and Ill have to look at this one you suggested), are the inputs internally pulled up to 5V and cause some funny action on my serial line? This is reasoning for looking at 3.3V devices first, though If I'm wrong here, please comment, Here is my logic for selecting an AND 1) operation is half duplex 2) during idle conditions, rx and tx (both RX and TX with respect to the master) lines are high, output is high 3) master starts transmitting, tx line goes low or high, rx stays high, output follows the TX line 4) slave responds, TX line stays high, RX line goes low and high, output follows the RX line The object is to make RX and TX line apear as on TX line transmitting all messages to a PC. The protocal we are using will work for sorting out master and slave messages. If my logic above is at fault, please comment Andy |
