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 <ea>,Dr:Dq 64/32
DIVS.L <ea>,Dr:Dq 64/32
MULU.L <ea>,Dr:Dq 32*32
MULS.L <ea>,Dr:Dq 32*32
MOVEP Dx,(d16,Ay) size = W or L
MOVEP (d16,Ay),Dx size = W or L
CHK2 <ea>,Rn size = B, W, or L
CMP2 <ea>,Rn size = B, W, or L
CAS2 Dc1:Dc2,Du1:Du2,(Rn1):(Rn2) size = W or L
CAS Dc,Du,<ea> 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 con-
dition 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
When the MC68060 encounters an unimplemented integer instruction, the MC68060 ini-
tiates exception processing at vector number 61. A type $0, four-word stack frame is cre-
ated. The stack frame’s stacked program counter (PC) points to the unimplemented integer
The M68060SP determines the instruction that caused the exception and emulates the
instruction using implemented integer instructions. This emulation includes the proper con-
dition 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 origi-
nal stack frame to the appropriate stack frame, and then branching to those system-supplied
exception handlers.
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