用C编写的摩托罗拉680x0模拟器.zip

Example M68k Program ==================== As an example, I'll build an imaginary hardware platform. The system is fairly simple, comprising a 68000, an input device, an output device, a non-maskable-interrupt device, and an interrupt controller. The input device receives input from the user and asserts its interrupt request line until its value is read. Reading from the input device's memory-mapped port will both clear its interrupt request and read an ASCII representation (8 bits) of what the user entered. The output device reads value when it is selected through its memory-mapped port and outputs it to a display. The value it reads will be interpreted as an ASCII value and output to the display. The output device is fairly slow (it can only process 1 byte per second), and so it asserts its interrupt request line when it is ready to receive a byte. Writing to the output device sends a byte to it. If the output device is not ready, the write is ignored. Reading from the output device returns 0 and clears its interrupt request line until another byte is written to it and 1 second elapses. The non-maskable-interrupt (NMI) device, as can be surmised from the name, generates a non-maskable-interrupt. This is connected to some kind of external switch that the user can push to generate a NMI. Since there are 3 devices interrupting the CPU, an interrupt controller is needed. The interrupt controller takes 7 inputs and encodes the highest priority asserted line on the 3 output pins. the input device is wired to IN2 and the output device is wired to IN1 on the controller. The NMI device is wired to IN7 and all the other inputs are wired low. The bus is also connected to a 1K ROM and a 256 byte RAM. Beware: This platform places ROM and RAM in the same address range and uses the FC pins to select the correct address space! (You didn't expect me to make it easy, did you? =) Schematic --------- NMI TIED SWITCH LOW | | | +-+-+-+ | | | | | +------------------------------------------------+ | | | | | | +------------------------------------+ | | | | | | | | | | +-------------+ | | |7 6 5 4 3 2 1| | | | | | | | INT CONTRLR | | | | | | | |i i i | | | |2 1 0 | | | +-------------+ | | | | | | | | | | +--------------------------------+--+ | | o o o | | | | | +--------------+ +-------+ +----------+ +---------+ +----------+ | I I I a | | | | | | r a i | | i | | 2 1 0 23 | | | | | | e c | | | | | | | | | | a k | | | | | | | | | | d | | | | | | | | | | | | | | M68000 | | ROM | | RAM | | IN | | OUT | | | | | | | | | | | | a9|--|a9 |--| |--| |--| | | a8|--|a8 |--| |--| |--| | | a7|--|a7 |--|a7 |--| |--| | | a6|--|a6 |--|a6 |--| |--| | | a5|--|a5 |--|a5 |--| |--| | | a4|--|a4 |--|a4 |--| |--| | | a3|--|a3 |--|a3 |--| |--| | | a2|--|a2 |--|a2 |--| |--| | | a1|--|a1 |--|a1 |--| |--| | | a0|--|a0 |--|a0 |--| |--| | | | | | | | | | | | | d15|--|d15 |--|d15 |--| |--| | | d14|--|d14 |--|d14 |--| |--| | | d13|--|d13 |--|d13 |--| |--| | | d12|--|d12 |--|d12 |--| |--| | | d11|--|d11 |--|d11 |--| |--| | | d10|--|d10 |--|d10 |--| |--| | | d9|--|d9 |--|d9 |--| |--| | | d8|--|d8 |--|d8 |--| |--| | | d7|--|d7 |--|d7 |--|d7 |--|d7 | | d6|--|d6 |--|d6 |--|d6 |--|d6 | | d5|--|d5 |--|d5 |--|d5 |--|d5 | | d4|--|d4 |--|d4 |--|d4 |--|d4 | | d3|--|d3 |--|d3 |--|d3 |--|d3 | | d2|--|d2 |--|d2 |--|d2 |--|d2 | | d1|--|d1 |--|d1 |--|d1 |--|d1 w | | d0|--|d0 |--|d0 |--|d0 |--|d0 r | | | | | | | | | | i a | | a F F F | | | | | | | | t c | |22 rW 2 1 0 | | cs | | cs rW | | | | e k | +--------------+ +-------+ +----------+ +---------+ +----------+ | | | | | | | | | | | | | | | | | | | | | | | | | +-------+ +-----+ | +---+ | | | | | | | IC1 | | IC2 | | |AND| | | | | | | |a b c d| |a b c| | +---+ | | | | | | +-------+ +-----+ | | | | | | | | | | | | | | | | | | +--+ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +-----)-)-+-)----)-)-+ | | | | | | +-------)-+---)----)-+ | | | | | +---------+-----)----+ | | | | | | | | | | +------------------+-----------+----------------------+ | | | +-----------------------------------------------------------+ IC1: output=1 if a=0 and b=1 and c=0 and d=0 IC2: output=1 if a=0 and b=0 and c=1 Program Listing (program.bin) ----------------------------- ``` INPUT_ADDRESS equ $800000 OUTPUT_ADDRESS equ $400000 CIRCULAR_BUFFER equ $c0 CAN_OUTPUT equ $d0 STACK_AREA equ $100 vector_table: 00000000 0000 0100 dc.l STACK_AREA * 0: SP 00000004 0000 00c0 dc.l init * 1: PC 00000008 0000 0148 dc.l unhandled_exception * 2: bus error 0000000c 0000 0148 dc.l unhandled_exception * 3: address error 00000010 0000 0148 dc.l unhandled_exception * 4: illegal instruction 00000014 0000 0148 dc.l unhandled_exception * 5: zero divide 00000018 0000 0148 dc.l unhandled_exception * 6: chk 0000001c 0000 0148 dc.l unhandled_exception *