example_asm.txt

这是一篇关于8位RISC CPU设计的文章

 ;-----------------------------------
 ; AN EXAMPLE ASSEMBLER PROGRAM 
 ;-----------------------------------

 ;----------------------------------------------
 ; define all the constants before using them 
 ;----------------------------------------------
 define off   0x00
 define on    0xff
 define bad   0xaa
 define good  0x55
 define rst_vector  0x1000
 define nmi_vector  0x1500
 define div0_vector 0x1700
 define int3_vector 0x1800
 
 ;--------------------------------------------------------------
 ; vector table - (4 bytes per vector, jmpa takes only 3 bytes)
 ;--------------------------------------------------------------
 org 0x0000       ; reset 
   jmpa al 0x1000

 org 0x0004       ; nmi
   jmpa al nmi_vector 

 org 0x0008       ; div 0
   jmpa al div0_vector

 org 0x000c       ; int 3
   jmpa al int3_vector
 
 ;-----------------------
 ; nmi service routine
 ;-----------------------
 org nmi_vector

   psh  r1
   psh  r2

   ldi  r1 on 
   ldi  r2 off
   lda  r0 0xfff0
   cmp  r1 
   jmpr eq turn_off
   sta  r1 0xfff0
   jmpr al s_end 

 turn_off:
   sta  r2 0xfff0

 s_end:
   pop  r2
   pop  r1
   ret

 ;------------------------
 ; some xyz subroutine
 ;------------------------
 org 0x3600

 some_xyz: 
  ldi r0 0x23
  sta r0 0xffe0
  ret  

 ;-----------------------------
 ; move_string subroutine
 ;------------------------------
 org 0x4000
 
 move_string:   
   psh  r1
   psh  r4
   psh  r5
   psh  r6
   psh  r7

   pmov a2 src_str  ; source string
   pmov a3 dst_str  ; destination string
   ldi  r1 0x00     ; end of the string

 loop_moves_sub:
   ldr  a2
   cmp  r1
   jmpr eq end_moves_sub 
   str  a3 
   inca a2
   inca a3
   jmpr al loop_moves_sub

 end_moves_sub:
   pop  r7
   pop  r6
   pop  r5
   pop  r4
   pop  r1
   ret
 
 ;------------------ 
 ; main program 
 ;------------------ 
 org rst_vector

   ldi r0 0xaa
   ldi r1 0xaa 
   ldi r2 0xff
   add r1
   cmp r2
   jmpa ne error

   ldi r1 0x01
   ldi r0 0x26
   ldi r2 0x27

 loop1:
   add r1
   cmp r2
   jmpa ne error
   inc r2
   jmpr ne loop1

   jmps al some_xyz
   ldi r0 good
   jmpa al finish

 ;-------------------
 ; define the data
 ;-------------------
 src_str:
   dcb "source_string"  
   dcb 0x00

 dst_str:
   dcb "destin_string"
   dcb 0x00

 no_strings_attached:
   dcb "this is string one"
   dcb "this is string two"
   dcb "THIS IS STRING three"

 other_bytes1:
   dcb 0x21 0x34 0x44 0x78 0xff

 other_bytes2:
   dcb 12 255 145 0

 table1: 
   dmem 10          ; allocate 10  bytes and initialized it with 0

 table2:
   dmem 300(0x11)   ; allocate 300 byes and initialize it with  0x11 
   dmem 22(02)      ; allocate 22  bytes and initialize it with 02
   dmem 0x10(0xff)  ; allocate 16  bytes and initialize it with 0xff 

  ; back to program
 
 error:
   ldi r0 bad

 finish:
   sta r0 0xffff
   end  ; not necessary to have a "end" directive. End of file also represents
        ; end of program.