Файл: Microcontroller Programming. Thi Micro Chip PIC (Julio Sanchez, 2007).pdf
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588 |
Chapter 16 |
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call |
delay_5 |
; Make sure not busy |
; Set up for data |
||
bcf |
PORTA,E_line |
; E line low |
bsf |
PORTA,RS_line |
; RS line high for data |
; Set up counter for 20 characters |
||
movlw |
D’20’ |
|
movwf |
count3 |
|
; Get display address from local variable pic_ad |
||
movf |
pic_ad,w ; First display RAM address to W |
|
movwf |
FSR |
; W to FSR |
getchar |
||
movf |
INDF,w ; get character from display RAM |
|
; location pointed to by file select |
||
; register |
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call |
send8 |
; 4-bit interface routine |
; Test for 16 characters displayed |
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decfsz |
count3,f |
; Decrement counter |
goto |
nextchar |
; Skipped if done |
return |
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nextchar: |
||
incf |
FSR,f |
; Bump pointer |
goto |
getchar |
|
;========================
;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 |
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swapf |
store1,w ; Swap nibbles in w |
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call |
merge4 |
||
movwf |
PORTD |
||
call |
pulseE |
; Send data to LCD |
|
call |
delay_125 |
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return |
|||
;========================== |
|||
; |
merge bits |
||
;========================== |
|||
Analog to Digital and Realtime Clocks |
589 |
;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 |
||
; the original value |
|||
movwf |
store2 |
; Save result |
in variable |
movf |
PORTD,w |
; Port-B to w |
register |
andlw |
b’00001111’ |
; Clear high nibble in Port-B |
|
; and preserve low nibble |
|||
iorwf |
store2,w ; OR two operands in w |
||
return |
|||
;==========================
;Set address register
;to LCD line 1 ;==========================
;ON ENTRY:
;Address of LCD line 1 in constant LCD_1
line1:
bcf |
PORTE,E_line |
; E line low |
bcf |
PORTE,RS_line |
; RS line low, set up for |
; control |
||
call |
delay_5 |
; busy? |
; Set to second display line |
||
movlw |
LCD_1 |
; Address and command bit |
call |
send8 |
; 4-bit routine |
; Set RS line for data |
||
bsf |
PORTE,RS_line |
; Setup for data |
call |
delay_5 |
; Busy? |
return |
||
;=============================== ; first text string procedure ;=============================== storeMS1:
590 |
Chapter 16 |
;Procedure to store in PIC RAM buffer the message
;contained in the code area labeled msg1
;ON ENTRY:
;variable pic_ad holds address of text buffer
;in PIC RAM
;w register hold offset into storage area
;msg1 is routine that returns the string characters
;and a zero terminator
;index is local variable that hold offset into
;text table. This variable is also used for
;temporary storage of offset into buffer
;ON EXIT:
;Text message stored in buffer
;
;Store offset into text buffer (passed in the w register)
;in temporary variable
movwf |
index |
; Store w in index |
; Store base address of text buffer in FSR |
||
movf |
pic_ad,w ; first display RAM address to W |
|
addwf |
index,w |
; Add offset to address |
movwf |
FSR |
; W to FSR |
; Initialize index for text string access |
||
movlw |
0 |
; Start at 0 |
movwf |
index |
; Store index in variable |
; w still = 0 |
||
get_msg_char: |
||
call |
msg1 |
; Get character from table |
; Test for zero terminator |
||
andlw |
0x0ff |
|
btfsc |
STATUS,Z ; Test zero flag |
|
goto |
endstr1 |
; End of string |
;ASSERT: valid string character in w
;store character in text buffer (by FSR)
movwf |
INDF |
; store in buffer by FSR |
|
incf |
FSR,f |
; increment buffer pointer |
|
; Restore table character counter from variable |
|||
movf |
index,w |
; Get value into w |
|
addlw |
1 |
; Bump to next character |
|
movwf |
index |
; Store table index in variable |
|
goto |
get_msg_char |
; Continue |
|
endstr1: |
|||
return |
|||
;Routine for returning message stored in program area
;Message has 10 characters
msg1:
addwf |
PCL,f |
; Access table |
retlw ‘P’
retlw ‘o’
Analog to Digital and Realtime Clocks |
591 |
|
retlw |
‘t’ |
|
retlw |
‘ ‘ |
|
retlw |
‘R’ |
|
retlw |
‘e’ |
|
retlw |
‘s’ |
|
retlw |
‘i’ |
|
retlw |
‘s’ |
|
retlw |
‘t’ |
|
retlw |
‘:’ |
|
retlw |
0 |
|
;========================
;blank buffer ;========================
;Procedure to store 20 blank characters in PIC RAM
;buffer starting at address stored in the variable
;pic_ad
blank20: |
|||
movlw |
D’20’ |
; Setup counter |
|
movwf |
count1 |
||
movf |
pic_ad,w ; |
First PIC RAM address |
|
movwf |
FSR |
; Indexed addressing |
|
movlw |
0x20 |
; ASCII space character |
|
storeit: |
|||
movwf |
INDF |
; |
Store blank character in PIC RAM |
; |
buffer using FSR register |
||
decfsz |
count1,f |
; Done? |
|
goto |
incfsr |
; |
no |
return |
; |
yes |
|
incfsr: |
|||
incf |
FSR,f |
; |
Bump FSR to next buffer space |
goto |
storeit |
||
;==============================
;binary to ASCII decimal
;conversion ;==============================
;ON ENTRY:
;w register has binary value in range 0 to 255
;ON EXIT:
;output variables asc100, asc10, and asc1 have
;three ASCII decimal digits
;Routine logic:
;The value 100 is subtracted from the source operand
;until the remainder is < 0 (carry cleared). The number
;of subtractions is the decimal hundreds result. 100 is
;then added back to the subtrahend to compensate
;for the last subtraction. Now 10 is subtracted in the
;same manner to determine the decimal tenths result.
592 |
Chapter 16 |
;The final remainder is the decimal units result.
;Variables:
; |
inNum |
storage for source operand |
;asc100 storage for hundreds position result
; |
asc10 |
storage for tenth position result |
||
; |
asc1 |
storage for unit position result |
||
; |
thisDig |
Digit counter |
||
bin2asc: |
||||
movwf |
inNum |
; Save copy of source value |
||
clrf |
asc100 |
; Clear hundreds storage |
||
clrf |
asc10 |
; Tens |
||
clrf |
asc1 |
; Units |
||
clrf |
thisDig |
|||
sub100: |
||||
movlw |
.100 |
|||
subwf |
inNum,f |
; Subtract 100 |
||
btfsc |
STATUS,C |
; Did subtract overflow? |
||
goto |
bump100 |
; No. Count subtraction |
||
goto |
end100 |
|||
bump100: |
||||
incf |
thisDig,f |
; Increment digit counter |
||
goto |
sub100 |
|||
; Store 100th digit |
||||
end100: |
||||
movf |
thisDig,w |
; Adjusted digit counter |
||
addlw |
0x30 |
; Convert to ASCII |
||
movwf |
asc100 |
; Store it |
||
; Calculate tenth position value |
||||
clrf |
thisDig |
|||
; Adjust minuend |
||||
movlw |
.100 |
; Minuend |
||
addwf |
inNum,f |
; Add value to minuend to |
||
; Compensate for last operation |
||||
sub10: |
||||
movlw |
.10 |
|||
subwf |
inNum,f |
; Subtract 10 |
||
btfsc |
STATUS,C |
; Did subtract overflow? |
||
goto |
bump10 |
; No. Count subtraction |
||
goto |
end10 |
|||
bump10: |
||||
incf |
thisDig,f |
;increment digit counter |
||
goto |
sub10 |
|||
; Store 10th digit |
||||
end10: |
||||
movlw |
.10 |
|||
addwf |
inNum,f |
; Adjust for last subtract |
||
movf |
thisDig,w |
; get digit counter contents |
||
addlw |
0x30 |
; Convert to ASCII |
||