main_asm.s

mpc55**系列芯片的例程 包括SCI,SPI,TIMER,FIT,EDMA等几乎所有功能的实现

# main_asm.s - Time Base example
# Rev 1 Aug 27 2004 S Mihalik
# Copyright Freescale Semiconductor, Inc 2004 All rights reserved.
# Compiled with CodeWarror 1.5 beta 1

  
.globl main_asm

.text
main_asm:	 
                      # INITIALIZE TIME BASE=0
  li      r4, 0       # Load immediate data of 0 to r4
  mttbu   r4		  	  # Move r4 to TBU 
  mttbl   r4          # Move r4 to TBL
											# ENABLE TIME BASE
  mfhid0  r5		  	  # Move from spr HID0 to r5 (copies HID0)
  li      r4, 0x4000  # Load immed. data of 0x4000 to r4
  or      r5, r4, r5  # OR r4 (0x0000 4000) with r4 (HID0 value)
  mthid0  r5          # Move result to HID0 
                      # EXECUTE SOME CODE
  nop
  nop
  nop
  nop
                      # RECORD TBL
  mftbl   r5          # Move TBL to r5 to store TBL value
  
  li	r4, 0
  li 	r5, 0
  mtmsr	r4
  mfmsr r4
  wrteei	1
  mfmsr	r5
  
  blr                 # (Set a breakpoint here and read r5)