Freescale Semiconductor MCF5480 - Manual (Page 749)

Programming Model
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 24-29
The base address for context save space is used to save variables and values being used by the MDE and
ADS. For each task, an area needs to be set aside for all relevant data to be saved until the task is called
again.
Figure 24-23. Task Descriptor Table Format
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Ta
sk 0
Task Descriptor Start Pointer
Task Descriptor End Pointer
Variable Table Pointer
Function Descriptor Base Address — PI S — I SP CW RL
Descriptor Address MDE
Status
— EU3
Status
Modified Variable Table Pointer
Base Address for Context Save Space
Literal
Base 0
Reserved Literal Base 1 Reserved
................... .
Ta
sk
n
Task Descriptor Start Pointer
Task Descriptor End Pointer
Variable Table Pointer
Function Descriptor Base Address — PI S — I SP CW RL
Descriptor Address MDE
Status
— EU3
Status
Modified Variable Table Pointer
Base Address for Context Save Space
Literal Base 0 Reserved Literal Base 1 Reserved
Note: For each task, the start pointer, end pointer, and variable table pointer are 32-bit values. For the task control bits, bits 31
through 8 are for the Function Descriptor Base Address, and bits 7 through 0 are control bits.
Table 24-20. Behavior of Task Table Control Bits
Bit Name Function
7 — Reserved
6 PI Precise Increment
0 Increments are allowed at any time the ADS can do it
1 Only increment at the end of an iteration
5 S Save all internal registers
0 Save only those internal registers currently used when doing a context save
1 Save all internal registers when doing a context save
4 — Reserved