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

;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:

;ON ENTRY:

;w contain value bits

;ON EXIT:

;w contains merged bits

merge4:

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

;blank buffer ;========================

;Procedure to store 16 blank characters in PIC RAM

;buffer starting at address stored in the variable

;pic_ad

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

;Set address register

;to LCD line 1 ;========================

;ON ENTRY:

;Address of LCD line 1 in constant LCD_1

line1:

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

;first text string procedure ;=============================== storeMS1:

;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

;ASSERT: valid string character in w

;store character in text buffer (by FSR)

;Routine for returning message stored in program area

;Message has 10 characters

msg1:

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

;BCD to ASCII decimal

;conversion ;==============================

;ON ENTRY:

;w register has two packed BCD digits

;ON EXIT:

;output variables asc10, and asc1 have

;two ASCII decimal digits

;Routine logic:

;The low order nibble is isolated and the value 30H

;added to convert to ASCII. The result is stored in

;the variable asc1. Then the same is done to the

;high-order nibble and the result is stored in the

;variable asc10

Bcd2asc:

;============================================================ ; 6355 RTC procedures ;============================================================ ;============================

;init RTC ;============================

;Procedure to initialize the real time clock chip. If chip

;is not initialized it will not operate and the values

;read will be invalid.

;Since the 6355 operates in BCD format the stored values must

;be converted to packed BCD.

;According to wiring diagram

;NJU6355 Interface for setting time:

;Writing to the 6355 requires that the CLK bit be held

;low while the IO and CE lines are high

;Seconds cannot be written to RTC. RTC seconds register

;is automatically initialized to zero