Файл: Microcontroller Programming. Thi Micro Chip PIC (Julio Sanchez, 2007).pdf
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Supplementary Programs |
737 |
|
addlw |
0x02 |
; Add 2 |
movwf |
scanCode |
|
incf |
newScan,f |
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return |
||
col3: |
||
movf |
rowCode,w |
; Row code to w |
addlw |
0x03 |
; Add 3 |
movwf |
scanCode |
|
incf |
newScan,f |
|
return |
||
;============================================================ ; initialize LCD for 4-bit mode ;============================================================ initLCD:
;Initialization for Densitron LCD module as follows:
;4-bit interface
;2 display lines of 16 characters each
;cursor on
;left-to-right increment
;cursor shift right
;no display shift
;=======================| |
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; |
set command mode |
| |
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;=======================| |
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bcf |
porte,E_line |
; E line low |
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bcf |
porte,RS_line |
; RS line low |
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bcf |
porte,RW_line |
; Write mode |
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call |
delay_125 |
; delay 125 microseconds |
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;***********************| |
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; |
FUNCTION SET |
| |
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;***********************| |
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movlw |
0x28 |
; 0 0 1 |
0 |
1 0 0 0 (FUNCTION SET) |
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; |
| |
| | |__ font select: |
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; |
| |
| | |
1 |
= 5x10 |
in 1/8 or 1/11 |
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; |
| |
| | |
0 |
= 1/16 |
dc |
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; |
| |
| |___ |
Duty cycle select |
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; |
| |
| |
0 |
= 1/8 or 1/11 |
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; |
| |
| |
1 |
= 1/16 |
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; |
| |
|___ Interface width |
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; |
| |
0 |
= 4 bits |
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; |
| |
1 |
= 8 bits |
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; |
|___ FUNCTION SET |
COMMAND |
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call |
send8 |
; 4-bit |
send routine |
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; Set 4-bit mode command must be repeated movlw 0x28
738 |
Appendix D |
call |
send8 |
;***********************| |
|
; DISPLAY AND CURSOR ON | |
|
;***********************| |
|
movlw |
0x0e |
; 0 0 0 0 1 1 1 0 (DISPLAY ON/OFF) |
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; |
| | | |___ Blink character |
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; |
| | | |
1 = on, 0 = off |
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; |
| | |___ Cursor on/off |
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; |
| | |
1 = on, 0 = off |
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; |
| |____ Display on/off |
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; |
| |
1 = on, 0 = off |
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; |
|____ COMMAND BIT |
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call |
send8 |
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;***********************| |
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; |
set entry mode |
| |
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;***********************| |
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movlw |
0x06 |
; 0 0 0 0 0 1 1 0 (ENTRY MODE SET) |
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; |
| | |___ display shift |
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; |
| | |
1 = shift |
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; |
| | |
0 = no shift |
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; |
| |____ cursor increment |
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; |
| |
1 = left-to-right |
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; |
| |
0 = right-to-left |
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; |
|___ COMMAND BIT |
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call |
send8 |
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;***********************| |
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; cursor/display shift |
| |
|||||
;***********************| |
||||||
movlw |
0x14 |
; 0 0 0 1 0 1 0 0 (CURSOR/DISPLAY |
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; |
SHIFT) |
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; |
| | | |_|___ don't care |
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; |
| |_|__ cursor/display shift |
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; |
| |
00 = cursor shift left |
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; |
| |
01 = cursor shift right |
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; |
| |
10 = cursor and display |
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; |
| |
shifted left |
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; |
| |
11 = cursor and display |
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; |
| |
shifted right |
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; |
|___ COMMAND BIT |
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call |
send8 |
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;***********************| |
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; |
clear display |
| |
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;***********************| |
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movlw |
0x01 |
; 0 0 0 0 0 0 0 1 (CLEAR DISPLAY) |
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; |
|___ |
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COMMAND BIT |
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Supplementary Programs |
739 |
|
call |
send8 |
|
; Per documentation |
||
call |
delay_5 |
; Test for busy |
return |
||
;=======================
;Procedure to delay
;42 microseconds ;======================= delay_125:
movlw |
D'42' |
; Repeat 42 machine cycles |
movwf |
count1 |
; Store value in counter |
repeat |
||
decfsz |
count1,f |
; Decrement counter |
goto |
repeat |
; Continue if not 0 |
return |
; End of delay |
;=======================
;Procedure to delay
;5 milliseconds ;======================= delay_5:
movlw |
D'42' |
; Counter = 41 |
|
movwf |
count2 |
; Store in variable |
|
delay |
|||
call |
delay_125 |
; Delay |
|
decfsz |
count2,f |
; 40 times = 5 milliseconds |
|
goto |
delay |
||
return |
; End of delay |
||
;======================== |
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; |
pulse E line |
||
;======================== |
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pulseE |
|||
bsf |
porte,E_line |
; Pulse E line |
|
Nop |
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bcf |
porte,E_line |
||
return |
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;=============================
;long delay sub-routine
;(for debugging) ;============================= long_delay
movlw |
D'200' |
; w delay count |
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movwf |
J |
; J = w |
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jloop: |
movwf |
K |
; |
K |
= |
w |
kloop: |
decfsz |
K,f |
; |
K |
= |
K-1, skip next if zero |
goto |
kloop |
|||||
740 |
Appendix D |
|
decfsz |
J,f |
; J = J-1, skip next if zero |
goto |
jloop |
|
return |
;========================
;send 2 nibbles in
;4-bit mode ;========================
;Procedure to send two 4-bit values to port B lines
;7, 6, 5, and 4. High-order nibble is sent first
;ON ENTRY:
;w register holds 8-bit value to send
send8:
movwf |
store1 |
; Save original value |
call |
merge4 |
; Merge with port B |
; Now w has merged byte |
||
movwf |
portd |
; w to port D |
call |
pulseE |
; Send data to LCD |
; High nibble is sent |
||
movf |
store1,w ; Recover byte into w |
|
swapf |
store1,w ; Swap nibbles in w |
|
call |
merge4 |
|
movwf |
portd |
|
call |
pulseE |
; Send data to LCD |
call |
delay_125 |
|
return |
||
;=================
;merge bits ;=================
;Routine to merge the 4 high-order bits of the
;value to send with the contents of port B
;so as to preserve the 4 low-bits in port B
;Logic:
;AND value with 1111 0000 mask
;AND port B with 0000 1111 mask
;Now low nibble in value and high nibble in
;port B are all 0 bits:
;value = vvvv 0000
;port B = 0000 bbbb
;OR value and port B resulting in:
; |
vvvv bbbb |
;ON ENTRY:
;w contain value bits
;ON EXIT:
;w contains merged bits
merge4:
andlw |
b'11110000' |
; |
ANDing with |
0 clears the |
; |
bit. ANDing |
with 1 preserves |