MC68EC030CFE25C Freescale Semiconductor, MC68EC030CFE25C Datasheet - Page 110

• Manufacturer Part Number: MC68EC030CFE25C
• Description: IC MPU 32BIT ENH 25MHZ 132-CQFP
• Manufacturer: Freescale Semiconductor

Specifications of MC68EC030CFE25C

• Processor Type: M680x0 32-Bit
• Speed: 25MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 132-CQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

3.5 INSTRUCTION EXAMPLES
3.5.1 Using the CAS and CAS2 Instructions
MOTOROLA
The following paragraphs provide examples of how to use selected instruc-
tions.
The CAS instruction compares the value in a memory location with the value
counters, history information, and globally shared pointers. The instruction
the new value. This provides security in single-processor systems, in multi-
tasking environments, and in multiprocessor environments. In a single-
the new value of a system variable. In a multiprocessor environment, the
The following code fragment shows a routine to maintain a count, in location
the count in register DO and stores the new count value in register D1. The
tion of the cycle copies the new count in SYS-CNTR into Do, and the routine
in a data register, and copies a second data register into the memory location
if the compared values are equal. This provides a means of updating system
uses an indivisible read-modify-write cycle; after CAS reads the memory
processor system, the operation is protected from instructions of an interrupt
routine. In a multitasking environment, no other task can interfere with writing
other processors must wait until the CAS instruction completes before ac-
cessing a global pointer.
SYS-CNTR, of the executions of an operation that may be performed by any
process or processor in a system. The routine obtains the current value of
CAS instruction copies the new count into SYS-CNTR if it is valid. However,
stored and the read-modify-write cycle of the CAS instruction, the write por-
location, no other instruction can change that location before CAS has written
if another user has incremented the counter between the time the count was
branches to repeat the test. The following code sequence guarantees that
SYS-CNTR is correctly incremented.
INC-LOOP
ADDQ.W
CAS.W
BNE
MOVE.W
MOVE.W
#1,D1
D0,D1,SYS_CNTR
INC-LOOP
SYS-CNTR,D0
D0,D1
MC68030 USER'S MANUAL
and increment it
get the old value of the counter
make a copy of it
if counter value is still the same, update it
if not, try again
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