Re: LCD question
Posted: Sat Jan 01, 2011 7:06 pm
The cosmac elf is just an example to illustrate the idea of how to test the LCD. The actual circuit should look something like above.
D0-D7 & RS are 10 way dip switches as suggested by zhenning. RP1 is an 8-way 10K resistors network to pull D0-D7 high. U1 is 4011 and sw1 is half of DPDT PB switch. "R/W" is tie low becos we only write to LCD. To display "HELLO", just do the following sequence:
D7----------D0 RS E
0 0 1 1 1 0 0 0 0 press once ;select 8 bit mode
0 0 0 1 1 0 0 0 0 press once ;set display shift
0 0 0 0 0 1 1 0 0 press once ;set display character mode
0 0 0 0 1 1 0 1 0 press once ;set disp on/off and cursor cmd
0 0 0 0 0 0 0 1 0 press once ;clear LCD display
0 1 0 0 1 0 0 0 1 press once ;ascii 'H'
0 1 0 0 0 1 0 1 1 press once ;ascii 'E'
0 1 0 0 1 1 0 0 1 press once ;ascii 'L'
0 1 0 0 1 1 0 0 1 press once ;ascii 'L'
0 1 0 0 1 1 1 1 1 press once ;ascii 'O'
Allen