;*************************************************************************
; arch/z80/src/ez80/ez80_saveusercontext.asm
;
; Copyright (C) 2008 Gregory Nutt. All rights reserved.
; Author: Gregory Nutt <spudmonkey@racsa.co.cr>
;
; Redistribution and use in source and binary forms, with or without
; modification, are permitted provided that the following conditions
; are met:
;
; 1. Redistributions of source code must retain the above copyright
; notice, this list of conditions and the following disclaimer.
; 2. Redistributions in binary form must reproduce the above copyright
; notice, this list of conditions and the following disclaimer in
; the documentation and/or other materials provided with the
; distribution.
; 3. Neither the name NuttX nor the names of its contributors may be
; used to endorse or promote products derived from this software
; without specific prior written permission.
;
; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
; FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
; COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
; BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
; OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
; AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
; LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
; ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
; POSSIBILITY OF SUCH DAMAGE.
;
;*************************************************************************
;**************************************************************************
; Global Symbols Imported
;**************************************************************************
;**************************************************************************
; Global Symbols Expported
;**************************************************************************
xdef _ez80_saveusercontext
;*************************************************************************
; Constants
;*************************************************************************
; Register save area layout
.if CONFIG_EZ80_Z80MODE
XCPT_I EQU 2*0 ; Offset 0: Saved I w/interrupt state in carry
XCPT_BC EQU 2*1 ; Offset 1: Saved BC register
XCPT_DE EQU 2*2 ; Offset 2: Saved DE register
XCPT_IX EQU 2*3 ; Offset 3: Saved IX register
XCPT_IY EQU 2*4 ; Offset 4: Saved IY register
XCPT_SP EQU 2*5 ; Offset 5: Offset to SP at time of interrupt
XCPT_HL EQU 2*6 ; Offset 6: Saved HL register
XCPT_AF EQU 2*7 ; Offset 7: Saved AF register
XCPT_PC EQU 2*8 ; Offset 8: Offset to PC at time of interrupt
.else
XCPT_I EQU 3*0 ; Offset 0: Saved I w/interrupt state in carry
XCPT_BC EQU 3*1 ; Offset 1: Saved BC register
XCPT_DE EQU 3*2 ; Offset 2: Saved DE register
XCPT_IX EQU 3*3 ; Offset 3: Saved IX register
XCPT_IY EQU 3*4 ; Offset 4: Saved IY register
XCPT_SP EQU 3*5 ; Offset 5: Offset to SP at time of interrupt
XCPT_HL EQU 3*6 ; Offset 6: Saved HL register
XCPT_AF EQU 3*7 ; Offset 7: Saved AF register
XCPT_PC EQU 3*8 ; Offset 8: Offset to PC at time of interrupt .endif
; Stack frame
FRAME_IY EQU 0 ; Location of IY on the stack
FRAME_IX EQU 2 ; Location of IX on the stack
FRAME_RET EQU 4 ; Location of return address on the stack
FRAME_REGS EQU 6 ; Location of reg save area on stack
SP_OFFSET EQU 6
;**************************************************************************
; Code
;**************************************************************************
segment CODE
;*************************************************************************
; Name: z80_saveusercontext
;*************************************************************************
_ez80_saveusercontext:
; Set up a stack frame
push ix ; Save IX and IY
push iy
ld ix, #0
add ix, sp ; IX = stack frame
; Fetch the address of the save area
ld de, FRAME_REGS(ix) ; DE = save area address
ld iy, #0
add iy, de ; IY = save area address
; Then save the registers
; Save the current interrupt state at offset 0
ld a, i ; Get interrupt state
push af
pop hl
ld XCPT_I(iy), hl ; Index 0: I w/interrupt state in parity/overflow
; Save BC at offset 1
ld XCPT_BC(iy), bc ; Index 1: BC
; DE is not preserved (Index 2)
; Save IX at offset 3
ld hl, FRAME_IX(ix) ; HL = Saved alue of IX
ld XCPT_IX(iy), hl ; Index 3: IX
; Save IY at index 4
ld hl, FRAME_IY(ix) ; HL = Saved value of IY
ld XCPT_IY(iy), hl ; Index 4: IY
; Save that stack pointer as it would be upon return in offset 5
ld hl, #SP_OFFSET ; Value of stack pointer on return
add hl, sp
ld XCPT_SP(iy), hl ; Index 5 SP
; HL is saved as the value 1 at offset 6
ld hl, #1
ld XCPT_HL(iy), hl ; Index 2: HL on return (=1)
; AF is not preserved (offset 7)
; Save the return address at index 8
ld hl, FRAME_RET(ix) ; HL = Saved return address
ld XCPT_PC(iy), hl ; Index 8: PC
; Return the value 0
ld hl, #0
pop iy
pop ix
ret
end
