ST20-C1 STMICROELECTRONICS [STMicroelectronics], ST20-C1 Datasheet - Page 83

• Manufacturer Part Number: ST20-C1
• Description: Instruction Set Reference Manual
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

7.7
7.7.1
Before multi-tasking operations can be performed, the scheduling queue must be
initialized. The scheduling queue is described in section 7.3. The queue must be
initialized by setting it to empty, which means setting the front pointer to empty:
7.7.2
A process consists of code, a work space area, a process control block and the values
for the Iptr, Wptr and Tdesc. To create a process, a large enough work space is
created, and a process control block of three words. It may be convenient to put all the
process control blocks together in one area of memory. For fast context switches and
minimal interrupt latency, process control blocks should be in on-chip memory.
The entry point for the process code is written into pw.Iptr of the process control
block. The address of the top of the work space is written into pw.Wptr of the process
control block, so the process code must adjust the initial Wptr down using ajw to
create space for local variables.
Initializing multi-tasking
Initializing the scheduling queue
ld MostNeg; ld SchedulerQptr; stnl q.FPtrLoc;
Creating and starting a process
mac_count
mac_buffer
mac_scale
mac_mode
global_interrupt_enable
local_interrupt_enable
overflo w
underflo w
carry
user_mode
interrupt_mode
trap_mode
sleep
reserved
start_next_task
timeslice_enable
timeslice_count
Field or bit
Table 7.3 Restarted process status register
As in previous process.
As in previous process.
As in previous process.
As in previous process.
As in previous process.
Set.
False.
False.
False.
True.
False.
False.
False.
Undefined.
False.
As in previous process.
MaxTimesliceCount.
Value
7 Multi-tasking
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