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;*************************************************************************
; arch/z80/src/z180/z180_saveusercontext.asm
;
; Copyright (C) 2012 Gregory Nutt. All rights reserved.
; Author: Gregory Nutt <gnutt@nuttx.org>
;
; 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.
;
;*************************************************************************
;*************************************************************************
; Constants
;*************************************************************************
; Register save area layout
.globl XCPT_I ; Offset 0: Saved I w/interrupt state in parity
.globl XCPT_BC ; Offset 1: Saved BC register
.globl XCPT_DE ; Offset 2: Saved DE register
.globl XCPT_IX ; Offset 3: Saved IX register
.globl XCPT_IY ; Offset 4: Saved IY register
.globl XCPT_SP ; Offset 5: Offset to SP at time of interrupt
.globl XCPT_HL ; Offset 6: Saved HL register
.globl XCPT_AF ; Offset 7: Saved AF register
.globl XCPT_PC ; Offset 8: Offset to PC at time of interrupt
; Stack frame
FRAME_IY == 0 ; Location of IY on the stack
FRAME_IX == 2 ; Location of IX on the stack
FRAME_RET == 4 ; Location of return address on the stack
FRAME_REGS == 6 ; Location of reg save area on stack
SP_OFFSET == 6
;*************************************************************************
; Name: z180_saveusercontext
;*************************************************************************
.area _CODE
_z180_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 e, FRAME_REGS(ix) ; HL = save area address
ld d, FRAME_REGS+1(ix) ;
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), l ; Offset 0: I w/interrupt state in parity
ld XCPT_I+1(iy), h
; Save BC at offset 1
ld XCPT_BC(iy), c ; Offset 1: BC
ld XCPT_BC+1(iy), b
; DE is not preserved (offset 2)
; Save IX at offset 3
ld l, FRAME_IX(ix) ; HL = Saved alue of IX
ld h, FRAME_IX+1(ix) ;
ld XCPT_IX(iy), l ; Offset 3: IX
ld XCPT_IX+1(iy), h ;
; Save IY at offset 4
ld l, FRAME_IY(ix) ; HL = Saved value of IY
ld h, FRAME_IY+1(ix) ;
ld XCPT_IY(iy), l ; Offset 4: IY
ld XCPT_IY+1(iy), h
; 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), l ; Offset 5 SP
ld XCPT_SP+1(iy), h
; HL is saved as the value 1 at offset 6
xor a ; A = 0
ld XCPT_HL+1(iy), a ; Offset 2: HL on return (=1)
inc a ; A = 1
ld XCPT_HL(iy), a ;
; AF is not preserved (offset 7)
; Save the return address in offset 8
ld l, FRAME_RET(ix) ; HL = Saved return address
ld h, FRAME_RET+1(ix) ;
ld XCPT_PC(iy), l ; Offset 8: PC
ld XCPT_PC+1(iy), h
; Return the value 0
xor a ; HL = return value of zero
ld l, a
ld h, a
pop iy
pop ix
ret
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