Page 66 - Making PIC Microcontroller Instruments and Controllers

56 GONTROLLI G THE OUTPUT AI{D READIIIG THE II{PUI

I
Control ing the Digital
and Analog Settings

ADCON1 = Analog to Digital CONtrol register#1.
The ADCONI=7.00000111 statement, or one lil(e it, is needed ior the 16F877A
because any PIC MCU processor that has any analog capabilities at all comes up in the
analog mode on reset and startup. This particular instruction puts all the analog pins on
po(s A and E into the digital mode. Since we need or y PORTE and PORTD for con
trolling the LCD, none of PORIA needs to be in digital mode. I am showing E 000001 I I
because all the examples used by nicroEngineering Labs in all their literature and on
their Web site use and suggest singthisvalue. See datasheet for more detajled infor-
mation. (The use of this register is also discussed in greater detail in Chapter 9.) If you
want 1o tum just the three available lines on PORTE to digital, you can use any binary
value from 010 to 111 inclusive.
The conlrol of the A-to D conversion capability is managed by the 4 low bits of
ADCONI. For our purposes, bit 0 and bit 3 are not relevant. See page 112 oI t}te
datasheet for detailed information on this.
"don't
Bit 0 is not relevant to the LCD operation (it is a care" bit).
Bit I and 2 must be set to 1 to make the two pots (A and E) digital.
"don't
Bit 3 is not relevant to the LCD operation (it, too, is a care" bit).
So ADCON I = '/.000001 I 0 or %0000011 I would be adeouate for our work. (We could
also have done this in decimal format with ADCON 1=6 or with ADCON1 =7.)

Writing Binary, Hex, and Decimal

Values to the LCD

The value of numbers written to the LCD can be specified with prefixes that determine
if the value wiil be display as a binary, a hexadecimal, or a decimal value. See the PBP
manual for details.

BIN specifies that the display will be binar).

HEX specifies ihat the display will be in hexadecimal format.
DEC specines that lhe display will be in decimal format.
"NMBR"
In hogram 5.5, the value of is set to 170 arbitrd dly (actually because it alter-
nates ls and 0s in binary fonmt). Any number below or equal to 255 could have been used.
Using BIN8 instead of BIN displays all 8 bits. Using Hex2 instead ofHEX displays both
hex digits. DEC5 can display all fivl. decimal digits because we are limited to 16 bits