add context_iar.S for SCONS

actually context_iar.S is the same as context_iar.asm
but context_iar.S is used for SCONS, and context_iar.asm is used for IAR

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1272 bbd45198-f89e-11dd-88c7-29a3b14d5316

libcpu/m16c/m16c62p/context_iar.S

+/*
+ * File      : context.asm
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2009, RT-Thread Development Team
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rt-thread.org/license/LICENSE
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2010-04-09     fify         the first version
+ * 2010-04-19     fify         rewrite rt_hw_interrupt_disable/enable fuction
+ * 2010-04-20     fify         move peripheral ISR to bsp/interrupts.s34 
+ *
+ * For       : Renesas M16C
+ * Toolchain : IAR's EW for M16C v3.401
+*/
+
+    RSEG        CSTACK
+
+    RSEG        ISTACK
+
+    RSEG        CODE(1)
+
+    EXTERN    rt_thread_switch_interrput_flag
+    EXTERN    rt_interrupt_from_thread
+    EXTERN    rt_interrupt_to_thread
+
+    PUBLIC    rt_hw_interrupt_disable
+    PUBLIC    rt_hw_interrupt_enable    
+    PUBLIC    rt_hw_context_switch_to
+    PUBLIC    rt_hw_context_switch
+    PUBLIC    rt_hw_context_switch_interrupt
+    PUBLIC    os_context_switch
+
+rt_hw_interrupt_disable
+    STC      FLG, R0    ;fify 20100419
+    FCLR     I
+    RTS
+
+rt_hw_interrupt_enable
+    LDC      R0, FLG    ;fify 20100419
+    RTS
+    
+    .EVEN
+os_context_switch:
+    PUSHM    R0,R1,R2,R3,A0,A1,SB,FB
+    CMP.W    #0,rt_thread_switch_interrput_flag
+    JEQ      exit
+    MOV.W    #0, rt_thread_switch_interrput_flag
+    MOV.W    rt_interrupt_from_thread, A0
+    STC      ISP, [A0]    
+    MOV.W    rt_interrupt_to_thread, A0
+    LDC      [A0], ISP
+exit
+    POPM     R0,R1,R2,R3,A0,A1,SB,FB             ; Restore registers from the new task's stack
+    REIT                                         ; Return from interrup    
+    
+/*
+ * void rt_hw_context_switch_to(rt_uint32 to);
+ * r0 --> to
+ * this fucntion is used to perform the first thread switch
+ */
+rt_hw_context_switch_to
+    MOV.W    R0, A0
+    LDC      [A0], ISP
+    POPM     R0,R1,R2,R3,A0,A1,SB,FB
+    REIT
+
+rt_hw_context_switch
+    CMP.W    #1,rt_thread_switch_interrput_flag
+    JEQ      jump1
+    MOV.W    #1,rt_thread_switch_interrput_flag
+    MOV.W    R0, rt_interrupt_from_thread
+jump1
+    MOV.W    R1, rt_interrupt_to_thread
+    INT      #0
+    RTS
+  
+rt_hw_context_switch_interrupt
+    CMP.W    #1,rt_thread_switch_interrput_flag
+    JEQ      jump
+    MOV.W    #1,rt_thread_switch_interrput_flag
+    MOV.W    R0, rt_interrupt_from_thread
+jump
+    MOV.W    R1, rt_interrupt_to_thread
+    RTS
+
+    END