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

;|_________________ 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 initally 1111 1110, is rotated left

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

; Set row mask for current 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, send, and receive data ;============================================================ ;============================================================

;At this point all keys have been tested.

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

;variable scanCode holds scan code

;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. Convert to ASCII by adding 0x30

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

;receive serial data ;========================== receive:

;Call serial receive procedure

call SerialRcv

;HOB of newData register is set if new data

;received

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

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

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

;in rowCode register). Sum is the scan code

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

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

; L O C A L P R O C E D U R E S

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

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

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

;init 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

;=======================|