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Diffstat (limited to 'interrupts.asm')
| -rw-r--r-- | interrupts.asm | 112 |
1 files changed, 0 insertions, 112 deletions
diff --git a/interrupts.asm b/interrupts.asm deleted file mode 100644 index cf2b195..0000000 --- a/interrupts.asm +++ /dev/null @@ -1,112 +0,0 @@ -;;; interrupt handling code - - ;; Current interrupt mode. IM 1 and friends will modify - ;; this, it can be any of 0, 1, 2. -int_mode: dc.b 0 - - ;; 0 if the emulated device doesn't want interrupts. - ;; 1 if interrupts are turned on. -int_enabled: dc.b 1 - - - ;; In interrupt mode 0, an interrupt will force a byte onto - ;; the data bus for the processor to execute. To handle - ;; those, the emulator will store the bus byte in int_opcode, - ;; which is followed by an absolute jump to the "next - ;; instruction". The value of int_jump will then be - ;; &int_opcode. - ;; - ;; This differs slightly from what I understand to be actual - ;; handling. The hardware will fetch an immediate argument to - ;; the interrupting instruction from the next location in - ;; memory. - ;; - ;; This emulator, on the other hand, will fetch the immediate - ;; argument from the JP instruction in the shim, and then - ;; dance off into la-la land. -int_opcode: dc.b 0 - dc.b $c3 ; JP immed.w -int_return: dc.w 0 ; the destination address - - - ;; This is the interrupt routine. It can come at any point - ;; during an instruction, though routines that use a5 (e.g. by - ;; calling C subroutines) will have to turn off interrupts. - ;; Routines that call into TIOS will have to remove this - ;; interrupt handler. -int_handler: - sub.l #4,a5 - rte - - -int_nevermind: - rts -do_interrupt: - ;; todo: make this file m4'd - add.l #INT_OFFSET,a5 ; clear the interrupt flag - - tst.b int_enabled ; 4 cycles - beq.b int_nevermind ; 8 cycles not taken - ;; Common case: interrupts enabled, fall through - - ;; Since this is an instruction all its own, we have D0, D1, - ;; and D2 available. - - pop.l a0 - - ;; Interrupts are most often in mode 1, then mode 2, and - ;; almost never in mode 0. - move.b int_mode,d0 - cmpi.b #1,d0 - beq int_do_mode2 - cmpi.b #2,d0 - beq int_do_mode1 - cmpi.b #1,d0 - beq int_do_mode0 - jmp (a0) - - ;; This routine emulates a mode 0 interrupt. - - ;; IM 0: A byte is placed on the bus and executed as if it - ;; were inline in the program. This emulator will put that - ;; byte into int_opcode and set epc (or int_jump) to point - ;; there. -int_do_mode0: - rts - - ;; This routine emulates a mode 1 interrupt. - - ;; IM 1: RST 38 is executed on every interrupt. This is what - ;; the TI-83+ uses almost all the time. -int_do_mode1: - jmp emu_op_ff - - - ;; This routine emulates a mode 2 interrupt. - - ;; IM 2: Vectored, the address jumped to is as follows: - ;; - ;; (I << 8) | (byte & 0xfe) - ;; - ;; where I is the I register, and byte is the byte that was - ;; found on the bus. -int_do_mode2: - rts - - ;; This routine emulates a non-maskable interrupt. -int_do_nmi: - rts - - - - - ;; This routine is used by the emulated DI instruction, which - ;; turns off emulator interrupts. -ints_stop: - rts - - ;; This routine is used by the emulated EI instruction, which - ;; turns on emulator interrupts. -ints_start: - rts - |