MC68030RC25C Freescale Semiconductor, MC68030RC25C Datasheet - Page 380

• Manufacturer Part Number: MC68030RC25C
• Description: IC MPU 32BIT ENHANCED 128-PGA
• Manufacturer: Freescale Semiconductor

Specifications of MC68030RC25C

• Processor Type: M680x0 32-Bit
• Speed: 25MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 128-PGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

MOTOROLA
/* The following are global to all routines
/* Symbolicly
Vallocate (SlzelnBytes, VlrtualAddressReturned, Status);
/* Symbolicly
Declare Lower_Table[O to Limit_Field] Based Record of
Declare Upper_Table[32] Record of
the table size). By convention, the first entry maps the supervisor address
space and has supervisor protection. The routine never modifies this first
space.
A routine similar to this that linearly extends (grows) a previously allocated
table entry) as a stack that grows downward from the highest address. If a
task needs several large stacks, a 16-Mbyte block can be used for each stack,
entry. The 31 entries after the first are available to be allocated as user address
memory block could be written. A stack is a good example. The operating
system can allocate the top of the memory (the thirty-second upper level
with a software flag set to indicate growth in a downward direction.
The logic of Vallocate is:
The code for Vallocate is:
2. Scan each upper table entry's lower page tables (where they exist)
3. If no space is found, see if the lower table is less than its maximum size
4. If still no space is found, use the next free upper table entry and initialize
1. Validate the request and calculate number of pages required.
5. Set allocated page entries to indicate virgin status (allocated, invalid,
6. Return status. If status is OK, also return virtual address.
and if the block can be allocated by expanding it at the end.
looking for an adequate group of unallocated pages.
its new lower level page table to allocate the block here.
and not swapped out).
define the lower level page table
define the upper level pointer table
Status=(invalid_unallocated,
Status=(unallocated, allocated),
Pointer;
Limit_Field=(O to 4k),
Pointer;
valid in memory),
invalid_paged o u t ,
invalid_virgin,
MC68030 USER'S MANUAL
/*not allocated to User
/*allocated but
/*allocated but
/*allocated and in memory
/*physical address or disk address of page
/* lower table
/* limff for
/*address
lower page table
of lower
here or not
paged out
not yet used
page table if allocated
9-79
°/
*/
*/
*/
°/
*/
*/
*/
*/
*/
*/
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