MC68030 Datasheet, PDF (392/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Coprocessor Interface Description
10.3.8 Operand CIR
When the coprocessor requests the transfer of an operand, the main processor performs
the transfer by reading from or writing to the 32-bit operand CIR. The offset from the base
address of the CIR set for the operand CIR is $10.
The MC68030 aligns all operands transferred to and from the operand CIR to the most
significant byte of this CIR. The processor performs a sequence of long-word transfers to
read or write any operand larger than four bytes. If the operand size is not a multiple of four
bytes, the portion remaining after the initial long-word transfers is aligned to the most
significant byte of the operand CIR. Figure 10-21 shows the operand alignment used by the
MC68030 when accessing the operand CIR.
31
23
BYTE OPERAND
15
7
0
NO TRANSFER
WORD OPERAND
THREE BYTE OPERAND
NO TRANSFER
LONG WORD OPERAND
TEN
BYTE
OPERAND
NO TRANSFER
Figure 10-21. Operand Alignment for Operand CIR Accesses
10.3.9 Register Select CIR
When the coprocessor requests the transfer of one or more main processor registers or a
group of coprocessor registers, the main processor reads the 16-bit register select CIR to
identify the number or type of registers to be transferred. The offset from the base address
of the CIR set for the register select CIR is $14. The format of this register depends on the
primitive that is currently using it. Refer to 10.4 Coprocessor Response Primitives.
10-32
MC68030 USER’S MANUAL
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