MC68EC000EI20 Freescale Semiconductor, MC68EC000EI20 Datasheet - Page 391

• Manufacturer Part Number: MC68EC000EI20
• Description: IC MPU 32BIT 20MHZ 68-PLCC
• Manufacturer: Freescale Semiconductor

Specifications of MC68EC000EI20

• Processor Type: M680x0 32-Bit
• Speed: 20MHz
• Voltage: 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 68-PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

FMOVEM
MOTOROLA
In this example, a convention is defined by which each called procedure is passed a
word mask in D7 that identifies all floating-point registers in use by the calling proce-
dure. Bits 15 – 8 identify the registers in the order FP0 – FP7, and bits 7 – 0 identify the
registers in the order FP7 – FP0 (the two masks are required due to the different trans-
fer order used by the predecrement and postincrement addressing modes). The code
used by the calling procedure consists of simply moving the mask (which is generated
at compile time) for the floating-point data registers currently in use into D7:
The entry code for all other procedures computes two masks. The first mask identifies
the registers in use by the calling procedure that are used by the called procedure (and
therefore saved and restored by the called procedure). The second mask identifies the
registers in use by the calling procedure that are used by the called procedure (and
therefore not saved on entry). The appropriate registers are then stored along with the
two masks:
If the second procedure calls a third procedure, a register mask is passed to the third
procedure that indicates which registers must not be altered by the third procedure.
This mask identifies any registers in the list from the first procedure that were not saved
by the second procedure, plus any registers used by the second procedure that must
not be altered by the third procedure.
Calling procedure...
Called procedure...
MOVE.W
BSR
MOVE.W
AND.W
FMOVEM
MOVE.W
EOR.W
MOVE.W
M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL
Move Multiple Floating-Point
#ACTIVE,D7
PROC_2
D7,D6
#WILL_USE,D7
registers.
D7, – (A7)
D7, – (A7)
D7,D6
registers.
D6, – (A7)
(MC6888X, MC68040)
Data Registers
in use.
Load the list of FP registers that are
Copy the list of active registers.
Generate the list of doubly-used
Save those registers.
Save the register list.
Generate the list of not saved active
Save it for later use.
Floating Point Instructions
FMOVEM
5-89