Task services
Cooperative task routines for resident workers and the registered pipe consumer.
Routine summary
| Routine | Input | Result |
|---|---|---|
| task_spawn | R0 = resident entry; R1 = initial argument | R0 = PID 1/2, or 0 on rejection/full; R1–R5 preserved. |
| task_yield | No arguments | R0–R5, SP, PC and supported PSW state restored on resumption. |
| task_sleep | R0 = 0–32767 ticks | R0 = 0 after the wait; 1 for an invalid duration or critical-section call. R1–R5 preserved. |
| task_self | No arguments | R0 = address of the current task-control block. |
| task_data | No arguments | R0 = private data address; R1 = 32. Both zero for PID 0/3. |
| task_beep | No arguments | R0 = 0 success or 1 I/O error; R1–R5 preserved. |
| task_exit | R0 = final result | Terminates PID 1/2 or restores the parent of PID 3; PID 0 receives error 1. |
task_spawn
task_spawn
R0 = resident entry; R1 = initial argument| Contract | Value |
|---|---|
| Entry address | 0x2236 |
| Returns | R0 = PID 1/2, or 0 on rejection/full; R1–R5 preserved. |
Allocates and initializes a background slot. Entry must be aligned and in the resident range, except the registered, verified pipe consumer while the pipe is active. Starts with R0 set to the argument, R1–R5 zero and interrupts enabled. Clears the slot’s private data; installs a return trampoline. FREE, DONE and FAULT slots may be reused. It is not a native-file loader.
task_yield
task_yield
No arguments| Contract | Value |
|---|---|
| Entry address | 0x20C2 |
| Returns | R0–R5, SP, PC and supported PSW state restored on resumption. |
Saves the calling context, checks stacks and selects the next READY context. In a busy controller transaction or with masked interrupt priority, returns without switching. The call is cooperative and must not be made from an ISR.
task_sleep
task_sleep
R0 = 0–32767 ticks| Contract | Value |
|---|---|
| Entry address | 0x21F8 |
| Returns | R0 = 0 after the wait; 1 for an invalid duration or critical-section call. R1–R5 preserved. |
Zero yields. Positive durations set a modular 16-bit deadline and put the caller in SLEEP before yielding. The scheduler makes it READY after the deadline; actual resumption depends on other tasks yielding.
task_self
task_self
No arguments| Contract | Value |
|---|---|
| Entry address | 0x2326 |
| Returns | R0 = address of the current task-control block. |
Returns a descriptor pointer, not a numeric PID. The descriptor is internal; applications should not rewrite its scheduling fields.
task_data
task_data
No arguments| Contract | Value |
|---|---|
| Entry address | 0x232C |
| Returns | R0 = private data address; R1 = 32. Both zero for PID 0/3. |
Returns the fixed private area of a background slot. Its contents survive yields and are zeroed when the slot is reused. There is no heap allocation.
task_beep
task_beep
No arguments| Contract | Value |
|---|---|
| Entry address | 0x2384 |
| Returns | R0 = 0 success or 1 I/O error; R1–R5 preserved. |
Provides the permitted buzzer path for background workers. It preserves the foreground controller-error state around the guarded tone transaction.
task_exit
task_exit
R0 = final result| Contract | Value |
|---|---|
| Entry address | 0x22FC |
| Returns | Terminates PID 1/2 or restores the parent of PID 3; PID 0 receives error 1. |
Closes an owned pipe read endpoint, records the final result and yields permanently for a worker. A normal RTS from a spawned worker reaches a trampoline that calls this routine. For PID 3, foreground cleanup restores the saved shell continuation.
Task-control block
Four 20-byte TCBs begin at 0x0760. Offsets are byte offsets; fields are little-endian words.
| Offset | Field |
|---|---|
| 0 | State; see multiprogramming state table. |
| 2 | Saved stack pointer. |
| 4 | RTC wake deadline modulo 65536. |
| 6 / 8 | Stack lower / upper-exclusive bounds. |
| 10 | Pointer to resident ASCIIZ name. |
| 12 | Application counter, unsigned 16-bit. |
| 14 | COUNT/PULSE limit; zero means continuous. |
| 16 | Final result. |
| 18 | Scheduler-selection count, unsigned 16-bit with wrap. |