Maxim-integrated MAXQ622 Manual do Utilizador descarregar pdf (Página 244)

MAXQ612/MAXQ622 User’s Guide

17-8 Maxim Integrated

17.4 ROM Example 1: Calling A Utility ROM Function Directly

This example shows the direct addressing method for calling utility functions, using the function moveDP1inc to read

a static string from code space. Note the equate UROM_MOVEDP1INC.

UROM_MOVEDP1INC EQU 087DBh

Text:

DB “Hello World!”,0 ; Define a string in code space.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; Function: PrintText

;; Description: Prints the string stored at the “Text” label.

;; Returns: N/A

;; Destroys: ACC, DP[1], DP[0], and GR.

;; Notes: This function assumes that DP[0] is set to word mode,

;; DP[1] is in byte mode, and the device has 16-bit accumulators.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

PrintText:

move DP[1], #Text ; Point to the string to display.

move ACC, DP[1] ; “Text” is a word address and we need a

sla ; byte address, so shift left 1 bit.

or #08000h ; Code space is mapped to 8000h when running

move DP[1], ACC ; from the ROM, so the address must be masked.

PrintText_Loop:

call UROM_MOVEDP1INC ; Fetch the byte from code space.

move ACC, GR

jump Z, PrintText_Done ; Reached the null terminator.

call PrintChar ; Call a routine to output the char in ACC

jump PrintText_Loop ; Process the next byte.

PrintText_Done:

ret

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Maxim-integrated MAXQ622 Manual do Utilizador Página 244