Page 65 - Making PIC Microcontroller Instruments and Controllers

LCD DISPIAY

andbllnking
in the LCD display
ipiiiiiiiiiry{i{:l Disprayins "HELLOWORLD"
(Continue,tl
DEFINE I,CD RVIBIT 2
DEFINE NCD-BITS A
DEFINE I,CD I,INES 2
DEFINE I.CD COMMANDI'S 2 0 0 0 ; delay in rnicio seconds
DEFINE I,CD_DATAUS 50 delay in nicro seconds

Set Lhe port directions. we are setting (nust set) all of PORTD
a o d q t l o I P O R T I " s o ' - p ! i . F v 6 r ' h o ! o t D o o - L d s o . l r . \ e p
l i n e s . T h - l o ! l b b l - i i D o o D / d l o e s e t d s - p - - s : . ^ e L c
a 4 high bit path Lo feed the LCD.)

PAUSE 500 araow ror LLU srarEup
ERISD = %00000000 rlnes !o ouEpur
TRISE = %00000000 ser all PORTE lines !o output
o o - - o - D r q i a c o - L - o - e g s L o r
r
A.DCONI=%00000111 needed for the 16F877A - see above and
below this nakes all of poris A and E
disitaL.
the main loop of the program
I,CDOUT SFE, 1 clear screen, go !o position 1
PAUSE 250 pause 0.2s seconds
LCDOUIF \HELI,oZ
LCDOUT tFE, SCo ; go to second 1lne, frrst position
I,CDOUT \![ORLDZ
PAUSE 250 ; Pause 0.25 seconds
Gctro LooP
EIID ; all progxans must end in END

Before we can write to the LCD. we have to define how the LCD is connected to the
MCU. Also, since the 16F877A has sone analog capahilities, it w,ill stah p atul rcset
in analog rnode, and has to be changed to digital mode (for PORTE onb in ow imme
diate case) before we can use its digital properttes.
The compiler manual tells us we have to specify the location of thl3 LCD and spec
ify the confit lines connected to it so the compiler can address the device properly. Doing
so lets us place the LCD wherever it's converfent for us when we design our own
devices (and the compiler will still be able find it). These variables are to be specified
in DEFINE statements before any of the rest of the program is written. (In thjs book,
we will always place the LCD at the same address locations used by the LAB Xl so
we can test all our programs for our insffuments on the LAB Xl when we need to,)
Program 5.4 demonstrates the most elementary control over oulpul to the LCD dis
play. Variations of these lines of code, and the addition of a few command codes, will
be used to write to the LCD in all our programs.
Not all the preceding DEFINE statements are needed on the LAB-XI, but when you
build your own devices, you will need to include them all to make sure nothing has been
omitted. You never know what state anMCU might start up in, so coverall yourbases.