piclist 1995\11\21\025143a >
Thread: Lcd Displays
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on Fri, 10 Nov 1995, John P. Hollinghsead wrote:

>I'm trying to get some code and so on together, for displaying to a
>ROHM 16x1 dot matric display.

>any help would be appreciated..

This is the set of commands for all LCD panel which are driven with the
HITACHI HD44780 controller, just check your panel to look at the chip.
LCD panel can driven by 4 or 8 bits. There is also 3 lines EN (Enable), D/I
(Data/Instruction) and R/W (Read/Write).
To connect with a minimum of wires you need 4+3 I/O lines in 4 bit mode.

Sequence for signals are as follow
              1st         2nd
              ____        ____
EN        ____|    |______|    |_____
             ____        ____
Data      ___|____|______|____|______
(4bit mode)   d4-d7        d3-d0

LCD panel is drived by an HITACHI controller HD44780 (panel ref: LM054,
LM016L, LM020L, LM041L, LM032L, LM044L, LM243A, LM027, LM23A, LM017L,
LM018L, etc ...).

Commands can be sent in frame of 4 or 8 bits. A reset put the panel in 8
bits mode. 4 bits mode use only bit B4,B5,B6 and B7.

Commands:
Exec.   DI RW b7 b6 b5 b4 b3 b2 b1 b0
1,52ms  0  0  0  0  0  0  0  0  0  1  Reset LCD Panel, Erase RAM
1,52ms  0  0  0  0  0  0  0  0  1  -  Cursor + AC=0, Display in origin position
37us    0  0  0  0  0  0  0  1 I/D S  Define cursor movment and shift display
37us    0  0  0  0  0  0  1  D  C  S  Display ON/OFF(D), cursor(C) and blonk
at                                       cursor position(B)
37us    0  0  0  0  0  1 S/L R/L-  -  Move the cursor and shift display
37us    0  0  0  0  1  DL N  F  -  -  Define bus length (DL), number of
line,                                         matrix font used (5x8 or 5x10)
37us    0  0  0  1  CG RAM Address    Define CG RAM Address
37us    0  0  1     DD RAM Address    Define DD RAM Address
0us     0  1  BF  Address counter AC  Read busy Flag & AC
37us    1  0     Write DATA           Write DATA into DD or CG RAM
37us    1  1     Read DATA            Read DATA from DD or CG RAM


Legend:
I/D  = 1: Increment, I/D = 0 : Decrement
S    = 1: Shift display
R/L  = 1: Shift to the right; R/L = 0 : Shift to the left
DL   = 1: 8 Bits; DL = 0 : 4 Bits
N    = 1: 2 or 4 lines; N = 0 : 1 line
F    = 1: 5x10 matrix; F = 0 : 5x8 matrix
BF   = 1: Busy; BF = 0 : free, can receive an instruction
DD Ram: Data Display RAM
CG Ram: Character Generator RAM

Execution time is given for a 270khz clock frequency (250-270Khz seems to be
the average value for current LCD panel).

RAM is not continuous RAM, mapping depend how many characters and line there
is in the panel. You can also define your own characters (CG RAM), only 8
CHR could be defined:

for 16x1:
1st line:  00h  01h ...  27h


for 16x2:
1st line:  00h  01h ...  27h
2nd line   40h  41h ...  67h

Regards,

      Philippe. <sonyedeKILLspamspam.....iway.fr>
<9511210750.AA02450@MIT.EDU>

See also: www.piclist.com/techref/lcds.htm?key=lcd
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