IF you mean she has 100 LED's to control, she will not be able to do it easy with an F84. You first of all need more output lines, and you will have to use shift registers to do so. First thing you have to see is how the LED's are controlled... is it 1 pin per lead (=100 pins), or is it a matrix style connection where there are pins for Led's in Column X, Row Y (like a co- ordinate system). Either way, you will need more IO lines - since it takes 2 lines per shift register, and assuming that you are using an 8-bit shift register, you can operate 4 SR's per port, or with an F84, 8 SR's in total (correct me if I'm wrong). 8 Shift register's will be able to control 8 bits each, so that is 64 bits in total. IF she is using a matrix style display (which I hope she is), then this will be ok since you will need only 25 lines... but if it is 1 pin per LED, then you might be better off with a PIC that can handle more IO. Quoting MarkIsrael@AOL.COM: > Please forgive this absolute dumb newbie question. > > I have a correspondent who is trying to control a > 20-by-5 LED display with a 16F84 PIC. She can make > 8 lights flash by writing to PORTB (she's sent me > her C code, which is quite similar to what's at > HREF="http://www- ee.eng.hawaii.edu/~sasaki/EE361/Fall01/quickovp.pdf">http://www- ee.eng.hawaii.edu/~sasaki/EE361/Fall01/quickovp.pdf > ), > but how can she write to the rest of the display? > > I feel I should be asking her some question about > the hardware connection, but I don't know enough > in this area even to formulate the question. > > Thanks for any help, > Mark Israel > MarkIsrael@aol.com > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > ---------------------------------------- This mail sent through www.mywaterloo.ca -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu