Freescale Semiconductor MC68881 - Move Multiple Floating-Point Data Registers Instruction Dialog

that since this instruction type cannot cause an exception, the PC bit is not set in any
primitive; thus, these instructions can be used to read or write the control registers without
overwriting the FPIAR contents.
The operation boxes that are marked
"R" or "W" indicate an operand read or write cycle,
respectively, by the MPU. Those operand transfer boxes that are shaded are optionally
executed, depending on the size and location of the source operand, For example, none
of the shaded boxes are executed for source operands that reside in the MPU registers.
7.5.1.5 MOVE MULTIPLE FPn (OPCLASS 110 and 111). This dialog is utilized for the move
multiple floating-point data registers instruction. The dialog for this instruction type is
shown in Figure 7-23, The first primitive of the dialog depends on the type of register list
specified by the instruction. If the static register list form of the instruction is used, the
first service request issued is the transfer multiple coprocessor registers primitive. For the
dynamic register list form, the first primitive requests the transfer of the main processor
data register that contains the register mask, and then the transfer multiple coprocessor
registers primitive is issued. In response to the transfer multiple coprocessor registers
primitive, the main processor reads the register list from the register select CIR and transfers
one register for each bit that is set in the list. (Note that the register list can be equal to
zero; in which case, no register transfer occurs.)
The read of the transfer single main processor register and transfer multiple coprocessor
registers primitives causes the response CIR encoding to be changed to the null primitive,
thus avoiding spurious request primitives in non-MC68020 or non-MC68030 based systems.
If the transfer single main processor register primitive is issued, the transfer multiple
coprocessor register primitive is not issued until the first service request is completed.
When the transfer multiple coprocessor register primitive service is complete, the main
processor is released to begin execution of the next instruction. Note that since this in-
struction type cannot cause an exception, the PC bit is not set in any primitive; thus, these
MC68020/MC68G31]
MC68881/MC68882
~- N ~--- ~ (DR=0) =-
--a m,j~ ..j v
~E SELECTED ~IY T.E REGISTER MASK
~ ~ REPEAT FOR EACH REGISTER
-- 0NLY IF A DYNAMIC REGISTER LIST IS USED
Figure 7-23. Move Multiple Floating-Point Data Registers Instruction Dialog
MC68881/MC68882 USER'S MANUAL
FREESCALE
7-27