概要

• MAX-IDE installation
• MAXQ Core Assembly Guide
• Development Tools Guide

RAMからコードを実行するメリット

消費電力の低減

メインプログラム空間に対する直接メモリアクセス

フラッシュメモリ全体の再書込みが可能

RAMからコードを実行するデメリット

コードスペースの制限

コードのミラーリングが必要

RAMへの直接アクセスが不可能

RAMから実行するコードのアセンブル

org 0080h

subOne:
   ....perform various calculations...
   ret

...

org 0300h

subTwo:
   call  subOne
   ...and so on...
   

subOne  equ  0A080h

org 0080h

; subOne
   ....perform various calculations...
   ret

...

org 0300h

subTwo:
   lcall  #subOne
   ...and so on...

RAMへのコードのコピー

org 0020h                    

copyToRAM:
   move    DPC,   #1Ch       ; Ensure all pointers are operating in word mode.
   move    DP[0], #8000h     ; Start of program flash from UROM's perspective.
   move    BP,    #0         ; Start of data memory.
   move    Offs,  #0         
   move    LC[0], #256       ; The Offs register limits us to a 256-word copy.
   lcall   UROM_copyBuffer

   move    DP[0], #8100h     ; Copy second half.
   move    BP,    #0100h
   move    Offs,  #0
   move    LC[0], #256
   lcall   UROM_copyBuffer

   ljump   #0A040h           ; Begin execution of code from RAM.


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Executing from RAM
;;

org 0040h

   move    LC[0], #1000
delayLoop:
   move    LC[1], #8000
   sdjnz   LC[1], $
   sdjnz   LC[0], delayLoop

;; Initialize serial port.

   move    SCON.6, #1        ; Set to mode 1 (10-bit asynchronous).
   move    SMD.1,  #1        ; Baud rate = 16 x baud clock
   move    PR, #009D4h       ; P = 2^21 * 9600/8.000MHz
   move    SCON.1, #0        ; Clear transmit character flag.

データ転送操作

;; Read the banner string from flash and output it over the serial port.  Since
;; we are running from RAM, we can read from the flash directly without having
;; to use the Utility ROM data transfer functions (moveDP0inc, etc...).

   move    SC.4,  #0
   move    DPC,   #0                  ; Set pointers to byte mode.
   move    DP[0], #(stringData * 2)   ; Point to byte address of string data.

stringLoop:
   move    Acc, @DP[0]++
   sjump   Z, stringEnd
   lcall   #TxChar
   sjump   stringLoop
stringEnd:
   move    DPC, #1Ch         ; Set pointers to word mode.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  This portion of the code (addresses 200h and higher) will remain in flash.

org 0200h

stringData:
   db      0Dh, 0Ah, "Executing code from RAM....", 00h

   scall   printVar
   scall   incrVar
   scall   printVar
   scall   incrVar
   scall   printVar
   scall   incrVar

   move    Acc, #0Dh
   lcall   #TxChar
   move    Acc, #0Ah
   lcall   #TxChar
   
   sjump   $


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Variables stored in RAM (program) space.  They can be read using the 
;;  Utility ROM data transfer functions (such as UROM_moveDP0) and written 
;;  using the writeDP0 function which remains in flash.
;;

varA:
   dw 'A'


;==============================================================================
;=
;=  printVar
;=
;=  Reads the varA RAM variable value and sends it over the serial port.
;=

printVar:
   move    DPC, #1Ch         ; Word mode
   move    DP[0], #varA      ; Variable's location in UROM data space
   lcall   UROM_moveDP0      ; Moves variable value into GR.
   move    Acc, GR
   lcall   #TxChar
   ret


;==============================================================================
;=
;=  incrVar
;=
;=  Reads the varA RAM variable value, adds 1 to it, and stores it back in RAM.
;=

incrVar:
   move    DPC, #1Ch         ; Word mode
   move    DP[0], #varA      ; Variable's location in UROM data space
   lcall   UROM_moveDP0      ; Moves variable value into GR.

   move    Acc, GR
   add     #1
   move    GR, Acc
   lcall   writeDP0

   ret



;==============================================================================
;=
;=  TxChar
;=
;=  Outputs a character to the serial port.
;=
;=  Inputs  : Acc.L - Character to send.
;=

org 01F0h
   move    SBUF, Acc         ; Send character.
TxChar_Loop:
   move    C, SCON.1         ; Check transmit flag.
   sjump   NC, TxChar_Loop   ; Stall until last transmit has completed.
   move    SCON.1, #0        ; Clear the transmit flag.
   ret


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  This portion of the code (addresses 200h and higher) will remain in flash.

org 0200h

stringData:
   db      0Dh, 0Ah, "Executing code from RAM....", 00h


;==============================================================================
;=
;=  WriteRAM
;=
;=  This is a routine that can be called by code running in the RAM to load
;=  a new value into a byte or word location in the RAM.
;=
;=  Inputs  : DP[0] - Location to write (absolute starting at 0000h) in RAM.
;=            GR    - Value to write to the RAM location.
;=  
;=  Notes   : DP[0] must be configured to operate in word or byte mode as
;=            desired before calling this function.  Following a call to this
;=            function, DP[0] must be refreshed before it is used to read data.
;=            

writeDP0:
   move    @DP[0], GR
   ret

結論