Page 152 - Making PIC Microcontroller Instruments and Controllers

You alo noi need the full datasheet. which is abolrt 40 pages long' bui you do need to
know the basic command set that controls the data tra$fer 1o your particular display
Thi s is usually provided by the organization you buy the LCD from and consists ol two
or three pages. You will need 1o refer to the dalasheet only if you want 1o creale specral
.t,*u"t"'..,_o. if yoo *nnt to display bargraphs and the like on tbe display The control
butyou don'tneed tobe famil
the Hitachi controller provides is very comprehensive,
iar with it to use a display effectively. Everything you need to know willbe covered in
this exerci se, but that should not keep you from learning as much as you can abou! con-
trolling the displays

Talkin to the LCD

The precerlilg confol codes allow you to configure the display' set display parameters'
set tie shape ind position of the cursol and so on To differentiate them from the char-
acter conmands, iach control code must be preceded by a hexadecimal FE or a deci'
mdl 254 to tell the confoller lhal the next character sent to lhe display will be a control
code. After receiving one control code and its argument' the Hitachi controller resets
to ihe data mode automaticaLly.
The controller suppots theASCII standard All uppercase and lowercase chamclers
ancl numerals are supported, as ale punctuation narks and the standad lext support char-
acters. (The controller also suppofts the display of a set of Japanese kana characte$')
It is ;1so possible to design your own font for use with the displays (though five
by seven [oi even ten] dots ;nd rwo lines does limit what can be done) All the infor-
mation needed to tlo so is contained in the Hitachi HD4'{780U datasheets Greek
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aDDlications.
The Hardware
Let's take a closer look at the LCD hardware.
Studv lhe datasheet that came with t}}e LCD. Find the pin-out descriptions and study
them. ihe 16 pins ar" osually identified as shown in Table 9 2'
displays' we find
Looking at ihe datasheet provided wirh the 2-line-by-16-characier
that the c;nfiol implementation can take Place if we have bodl a poft and a few lines
available to control the LCD. It does not have to be controlled from any predefined lines'
We can select all the lines needed to support the display in our project and they can be
on any port we have available The only requirement seems to be that the four/eight data
line be either the contiguous top, or the bottom half, of a po This is not a paticularly
demanrling requirement other lban that it means the smaller PICS cannot be used if we
will retlLrire many I/o lines in our project The other thtee lines needed can be on any
of the other ports. and do not all need to be on lhe same pol1 Since we are considering