;**************************************************************************
; arch/z80/src/z180/z180_vectcommon.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.
;
;**************************************************************************
.title NuttX for the Z180
.module z180_vectcommon
;**************************************************************************
; Constants
;**************************************************************************
; Register save area layout
XCPT_I == 0 ; Offset 0: Saved I w/interrupt state in carry
XCPT_BC == 2 ; Offset 1: Saved BC register
XCPT_DE == 4 ; Offset 2: Saved DE register
XCPT_IX == 6 ; Offset 3: Saved IX register
XCPT_IY == 8 ; Offset 4: Saved IY register
XCPT_SP == 10 ; Offset 5: Offset to SP at time of interrupt
XCPT_HL == 12 ; Offset 6: Saved HL register
XCPT_AF == 14 ; Offset 7: Saved AF register
XCPT_PC == 16 ; Offset 8: Offset to PC at time of interrupt
;**************************************************************************
; Global symbols used
;**************************************************************************
.globl _up_doirq ; Interrupt decoding logic
;**************************************************************************
; Vector Handlers
;**************************************************************************
.area _CODE
up_int1:: ; Vector offset 0: External /INT1
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #9 ; 9 = Z180_INT1
jr _up_vectcommon ; Remaining RST handling is common
up_int2:: ; Vector offset 2: External /INT2
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #10 ; 10 = Z180_INT2
jr _up_vectcommon ; Remaining RST handling is common
up_prt0:: ; Vector offset 4: PRT channel 0
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #11 ; 11 = Z180_PRT0
jr _up_vectcommon ; Remaining RST handling is common
up_prt1:: ; Vector offset 6: PRT channel 1
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #12 ; 12 = Z180_PRT1
jr _up_vectcommon ; Remaining RST handling is common
up_dma0:: ; Vector offset 8: DMA channel 0
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #13 ; 13 = Z180_DMA0
jr _up_vectcommon ; Remaining RST handling is common
up_dma1:: ; Vector offset 8: DMA channel 1
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #14 ; 14 = Z180_DMA1
jr _up_vectcommon ; Remaining RST handling is common
up_csio:: ; Vector offset 12: Clocked serial I/O
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #15 ; 15 = Z180_CSIO
jr _up_vectcommon ; Remaining RST handling is common
up_asci0:: ; Vector offset 14: Async channel 0
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #16 ; 16 = Z180_ASCI0
jr _up_vectcommon ; Remaining RST handling is common
up_asci1:: ; Vector offset 16: Async channel 1
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #17 ; 17 = Z180_ASCI1
jr _up_vectcommon ; Remaining RST handling is common
up_unused:: ; Vector offset 18: Unused
; Save AF on the stack, set the interrupt number and jump to the
; common reset handling logic.
; Offset 8: Return PC is already on the stack
push af ; Offset 7: AF (retaining flags)
ld a, #18 ; 18 = Z180_UNUSED
jr _up_vectcommon ; Remaining RST handling is common
;**************************************************************************
; Common Interrupt handler
;**************************************************************************
_up_vectcommon::
; Create a register frame. SP points to top of frame + 4, pushes
; decrement the stack pointer. Already have
;
; Offset 8: Return PC is already on the stack
; Offset 7: AF (retaining flags)
;
; IRQ number is in A
push hl ; Offset 6: HL
ld hl, #(3*2) ; HL is the value of the stack pointer before
add hl, sp ; the interrupt occurred
push hl ; Offset 5: Stack pointer
push iy ; Offset 4: IY
push ix ; Offset 3: IX
push de ; Offset 2: DE
push bc ; Offset 1: BC
ld b, a ; Save the reset number in B
ld a, i ; Parity bit holds interrupt state
push af ; Offset 0: I with interrupt state in parity
di
; Call the interrupt decode logic. SP points to the beginning of the reg structure
ld hl, #0 ; Argument #2 is the beginning of the reg structure
add hl, sp ;
push hl ; Place argument #2 at the top of stack
push bc ; Argument #1 is the Reset number
inc sp ; (make byte sized)
call _up_doirq ; Decode the IRQ
; On return, HL points to the beginning of the reg structure to restore
; Note that (1) the arguments pushed on the stack are not popped, and (2) the
; original stack pointer is lost. In the normal case (no context switch),
; HL will contain the value of the SP before the arguments were pushed.
ld sp, hl ; Use the new stack pointer
; Restore registers. HL points to the beginning of the reg structure to restore
ex af, af' ; Select alternate AF
pop af ; Offset 0: AF' = I with interrupt state in carry
ex af, af' ; Restore original AF
pop bc ; Offset 1: BC
pop de ; Offset 2: DE
pop ix ; Offset 3: IX
pop iy ; Offset 4: IY
exx ; Use alternate BC/DE/HL
ld hl, #-2 ; Offset of SP to account for ret addr on stack
pop de ; Offset 5: HL' = Stack pointer after return
add hl, de ; HL = Stack pointer value before return
exx ; Restore original BC/DE/HL
pop hl ; Offset 6: HL
pop af ; Offset 7: AF
; Restore the stack pointer
exx ; Use alternate BC/DE/HL
ld sp, hl ; Set SP = saved stack pointer value before return
exx ; Restore original BC/DE/HL
; Restore interrupt state
ex af, af' ; Recover interrupt state
jp po, nointenable ; Odd parity, IFF2=0, means disabled
ex af, af' ; Restore AF (before enabling interrupts)
ei ; yes
reti
nointenable::
ex af, af' ; Restore AF
reti
