Файл: Microcontroller Programming. Thi Micro Chip PIC (Julio Sanchez, 2007).pdf

;============================================================

; M A I N P R O G R A M

;============================================================

;Wiring:

;LCD data to port D, lines 0 to 7

;E line -> port E, 1

;RW line -> port E, 2

;RS line -> port E, 0

;Set porte D and E for output

;First, initialize port B by clearing latches clrf STATUS

clrf PORTB

;Select bank 1 to tris port D for output Bank1

;Tris port D for output. Port D lines 4 to 7 are wired

;to LCD data lines. Port D lines 0 to 4 are wired to LEDs. movlw B'00000000'

;By default port A lines are analog. To configure them

;as digital code must set bits 1 and 2 of the ADCON1

;register (in bank 1)

;7 6 5 4 3 2 1 0

;| | | | |_|_|_|_____ switch rows (output)

;|_|_|_|_____________ switch columns (input)

;rows must be defined as output and columns as input

;|__________________________ RBPU (Pullup enable)

;Back to bank 0 Bank0

;Clear all output lines movlw b'00000000' movwf portd

;========================

;scan keypad ;========================

;Keypad switch wiring:

;|_________________ port B7 |

;Switches are connected to port B lines

;Clear scan code register

clrf scanCode ;============================

;scan keypad and display ;============================ keyScan:

;Port B, lines are wired to pushbutton switches, as follows:

;7 6 5 4 3 2 1 0

;| | | | |_|_|_|_____ switch rows (output)

;|_|_|_|_____________ switch columns (input)

;Keypad processing:

;switch rows are successively grounded (row = 0)

;Then column values are tested. If a column returns 0

;in a 0 row, that switch is down.

;Initialize row code addend

;Initialize row eliminator mask:

;The row mask is ANDed with the key mask to successively

;mask-off each row, for example:

;The row mask, which is initially 1111 1110, is rotated left

;through the carry in order to mask off the next row

;=========================

;shift row mask ;=========================

;Set the carry flag

;=========================

;end of keypad? ;=========================

;Test for last key row (maximum count is 4)

decfsz rowCount,f ; Decrement counter goto keyLoop

;===========================================================

;=========================================================== ; display scan code ;=========================================================== ;===========================================================

;At this point all keys have been tested.

;Variable newScan = 0 if no new scan code detected, else

;variable scanCode holds scan code

; At this point a new scan code is detected

;If scan code is in the range 0 to 9, that is, a decimal

;digit, then ASCII conversion consists of adding 0x30.

;If the scan code represents one of the hex letters

;(0xa to 0xf) then ASCII conversion requires adding

;0x37

;if w from 0 to 9 then 9 - w = positive (c flag = 1)

;if w = 0xa then 9 - 10 = -1 (c flag = 0)

;if w = 0xc then 9 - 12 = -2 (c flag = 0)

;At this point scan code is a decimal digit in the

;range 0 to 9. Conver to ASCII by adding 0x30

;==========================

;calculate scan code ;==========================

;The column position is added to the row code (stored

;in rowCode register). Sum is the scan code