使用数据指针，以读/写SRAM

Introduction

Getting Started

Data Pointer Overview

move DPC,   #2		;(explicit) selection of BP as the active pointer
move DP[1], DP[1]		;(implicit) selection of DP[1]; set SDPS1: 0=01b
move OFFS,  src		;(implicit) selection of BP; set SDPS1=1
move @DP[0],src		;(implicit) selection of DP[0]; set SDPS1:0=00b

Increment/Decrement Data Pointer

move NUL, @DP[0]++		;increment DP[0]
move NUL, @DP[1]-- 		;decrement DP[1]
move NUL, @BP[OFFS++] 	;increment Frame Pointer Base + Offset + 1

move @++DP[0], A[1]		;increment address and store A[1] at new address
;Note: Only the pre-increment/decrement can be ;used
				;when writing to memory
move A[1], @DP[1]--		;Reads value from DP[1] and store in A[1] then
				;decrement
;Note: Only the post-increment/decrement can be
;used
				;when reading from memory

Code Example

1. Move 2 words to SRAM using DP[0]. 5555h is moved to the first word of SRAM, referenced by int_Var1; AAAAh is moved to the second word of SRAM, referenced by int_Var2. Var_1 and Var_2 are read back from SRAM into accumulator A[0] and A[1].
   
   

   int_Var1 EQU 0h		;address of int_Var1 to the first byte of SRAM
   int_Var2 EQU 1h		;address of int_Var2 to the second byte of SRAM
   
   main:
   move DPC,    #4h		;Set DP[0] to word mode
   					;Must be set active before using
   
   move DP[0],  #int_Var1	;Load address of int_Var1 into DP[0]
   					;also activated DP[0]
   move @DP[0], #5555h		;write 5555h to SRAM at address of int_Var1
   
   move DP[0],  #int_Var2	;Load address into of int_Var1 into DP[0]
   move @DP[0], #0AAAAh		;Writes AAAAh to SRAM at address of int_Var2
   
   move DP[0],  #int_Var1	;Load address of int_Var1 into DP[0]
   move A[0],  @DP[0]		;Reads from address of int_Var1
   
   move DP[0], #int_Var2	;Load address of int_Var2 into DP[0]
   move A[1],  @DP[0]		;Reads from address of int_Var2
   
   move  AP,   #0        	;select accumulator 0
   and  A[1]			;AND the A[1] and A[0] and store in A[0]
   end
   

   
   
2. Move 2 bytes to SRAM using DP[1]. 55h is moved to the first byte of SRAM, referenced by int_Var1; AAh is moved to the second byte of SRAM, referenced by int_Var2. Var_1 and Var_2 are read back from SRAM into accumulator A[0] and A[1].
   
   

   int_Var1 EQU 0h		;address of int_Var1 to the first word of SRAM
   int_Var2 EQU 1h		;address of int_Var2 to the second word of SRAM
   
   main:
   move DPC,    #0h		;Set DP[1] to byte mode
   					;Must be set active before using
   
   move DP[1],  #int_Var1	;Load address of int_Var1 into DP[1]
   					;also activated DP[1]
   move @DP[1], #55h		;write 55h to SRAM at address of int_Var1
   
   move DP[1],  #int_Var2	;Load address into of int_Var1 into DP[1]
   move @DP[1], #0AAh		;Writes AAh to SRAM at address of int_Var2
   
   move DP[1],  #int_Var1	;Load address of int_Var1 into DP[1]
   move A[0],   @DP[1]		;Reads from address of int_Var1
   
   move DP[1],  #int_Var2	;Load address of int_Var2 into DP[1]
   move A[1],   @DP[1]		;Reads from address of int_Var2
   
   move  AP,    #0       	;select accumulator 0
   and  A[1]			;AND the A[1] and A[0] and store in A[0]
   end
   

   
   
3. Move 2 words to SRAM using BP[Offs]. 5555h is moved to the first word of SRAM, referenced by int_Var1; AAAAh is moved to the second word of SRAM, referenced by int_Var2. Var_1 and Var_2 are read back from SRAM into accumulator A[0] and A[1].
   
   

   int_Var1 EQU 0h		;address of int_Var1 to the first word of SRAM
   int_Var2 EQU 1h		;address of int_Var2 to the second word of SRAM
   
   main:
   move DPC, #10h			;Set BP[OFFS] to word mode
   move BP,  #0h			;Sets BP to 0 and activates BP[OFFS]
   
   move OFFS, #int_Var1		;Load address of int_Var1 into OFFS
   move @BP[OFFS], #5555h	;write to 5555h to SRAM at address of int_Var1
   
   move OFFS, #int_Var2		;Load address into of int_Var1 into OFFS
   move @BP[OFFS], #0AAAAh 	;Writes AAAAh to SRAM at address of int_Var2
   
   move OFFS, #int_Var1		;Load address of int_Var1 into OFFS
   move A[0], @BP[OFFS]		;Reads from address of int_Var1
   
   move OFFS, #int_Var2		;Load address of int_Var2 into OFFS
   move A[1], @BP[OFFS]		;Reads from address of int_Var2
   
   move AP,   #0         	;select accumulator 0
   and  A[1]			;AND the A[1] and A[0] and store in A[0]
   end
   

Invalid Data Pointer Instruction

move DP[0], DP[0]
move A[1], @DP[0]
move A[2], @DP[1]

move DP[0], DP[0]
move A[1], @DP[0]
move DP[1], DP[1]
move A[2], @DP[1]

move BP[OFFS], #0h

move BP, #0h
move OFFS, #0h

move @DP[0]++, A[0]

move @++DP[0], A[0]

move A[0], @++DP[0]

move A[0], @DP[0]--

move @++DP[0], @DP[0]++

move A[1], @DP[0]++
move @++DP[0], A[1]

move @DP[0]++, A[1]

move @DP[0], A[1]
move NUL, @DP[0]++

move A[0], @--DP[0]

move NUL, @DP[0]--
move A[0], @DP[0]

Relevant Links

• MAXQ Home Page
• MAXQ Family User's Guide
• MAXQ2000 User's Guide Supplement
• Dallas Semiconductor Microcontroller Support Forum