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MC68060 Software Package
library that can be used to avoid these unimplemented instructions for new programs that
can be recompiled.
The unimplemented integer instructions include 64-bit divide and multiply, move peripheral
data, CMP2, CHK2, and CAS2. In addition, CAS used with a misaligned effective address
is also unimplemented. Refer to the M68000 Family Programmer’s Reference Manual
(M68000PM/AD) for details on the operation of these instructions. The unimplemented
integer instructions are:
DIVU.L
DIVS.L
MULU.L
MULS.L
MOVEP
MOVEP
CHK2
CMP2
CAS2
CAS
<ea>,Dr:Dq
<ea>,Dr:Dq
<ea>,Dr:Dq
<ea>,Dr:Dq
Dx,(d16,Ay)
(d16,Ay),Dx
<ea>,Rn
<ea>,Rn
Dc1:Dc2,Du1:Du2,(Rn1):(Rn2)
Dc,Du,<ea>
64/32 ⇒ 32r,32q
64/32 ⇒ 32r,32q
32*32 ⇒ 64
32*32 ⇒ 64
size = W or L
size = W or L
size = B, W, or L
size = B, W, or L
size = W or L
size = W or L, misaligned <ea>
C.2.1 Integer Emulation Results
Numerical and condition code results produced by the MC68060ISP (see C.2.2 Module 1:
Unimplemented Integer Instruction Exception (MC68060ISP)) are equivalent to those in
previous M68000 family processors. In addition, as with the MC68060 hardware, if any condition code bits are stated as undefined for the exceptional instruction, then they remain
unchanged from the previous instruction.
C.2.2 Module 1: Unimplemented Integer Instruction Exception
(MC68060ISP)
When the MC68060 encounters an unimplemented integer instruction, the MC68060 initiates exception processing at vector number 61. A type $0, four-word stack frame is created. The stack frame’s stacked program counter (PC) points to the unimplemented integer
instruction.
The M68060SP determines the instruction that caused the exception and emulates the
instruction using implemented integer instructions. This emulation includes the proper condition code effects as produced by the instruction if it had been implemented in hardware.
No floating-point instructions are used within this module (to ensure that this module can be
used for the MC68LC060 and MC68EC060).
When emulating the unimplemented integer instructions, there are conditions that require
the M68060SP to emulate an exception. The M68060SP emulates an exception by cleaning
up the stack to the conditions prior to executing the exception handler, converting the original stack frame to the appropriate stack frame, and then branching to those system-supplied
exception handlers.
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M68060 USER’S MANUAL
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