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295 lines of unfinished scheduler
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297
scheduler.asm
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297
scheduler.asm
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;; scheduler
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;
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; Because we want want to be able use multible thread, we need a scheduler.
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; This scheduler is supposed to support up to 5 threads.
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;
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;;
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;; global memory map
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;
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; $000
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; G P R
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; $01F
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; $020
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; I O R
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; $05F
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; $060
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; SRAM
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; $060
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; 192 bytes of scheduler memory
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; $102
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; $103
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; 1069 bytes of heap
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; $52F
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; $530
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; 639 bytes of stack
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; $62F
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; $62F
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;
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;;
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; this a ATmega16 specific
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.equ heap_start = 0x103 ; starting address of heap
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.equ heap_end = 0x52F ; ending address of heap
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.equ scheduler_global_active = 0x060 ; address of active-thread-cell
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.equ scheduler_global_number = 0x061 ; address of thread-number-cell
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.equ scheduler_global_maxnum = 0x004 ; maximal number of thread
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.equ scheduler_global_statu1 = 0x062 ; address of global-status-cell 1
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.equ scheduler_global_statu2 = 0x063 ; address of global-status-cell 2
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.equ scheduler_global_unused = 0x064 ; start address of unused block
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.equ scheduler_global_thread = 0x06B ; starting address of scheduler memory
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.equ scheduler_global_length = 0x026 ; length of thread in scheduler memory
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.equ scheduler_global_lastad = 0x102 ; last address of scheduler memory
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.equ scheduler_global_stacks = 0x530 ; start address of stacks
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.equ scheduler_offset_stacks = 0x040 ; length of 1 stack
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.equ scheduler_offset_instat = 0x000 ; offset of internal sr in scheduler memory
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.equ scheduler_offset_instrh = 0x001 ; offset of iph in scheduler memory
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.equ scheduler_offset_instrl = 0x002 ; offset of ipl in scheduler memory
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.equ scheduler_offset_status = 0x003 ; offset of sr in scheduler memory
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.equ scheduler_offset_stackh = 0x004 ; offset of sph in scheduler memory
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.equ scheduler_offset_stackl = 0x005 ; offset of spl in scheduler memory
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.equ scheduler_offset_gprsta = 0x006 ; start offset of gpr in scheduler momory
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.equ scheduler_offset_gprend = 0x025 ; end offset of gpr in scheduler memory
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;; scheduler memory
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;
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; We need to save the number of threads, the number of the active thread
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; and some other things.
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; For every thread we need to save:
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; - the instruction pointer (2 byte)
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; - the status register (1 byte)
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; - the stack pointer (2 byte)
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; - all 32 pgr
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; - plus 1 byte of status-values for the scheduler
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; => 38 bytes -> $26; starting at $06B
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; so: the sp of our thread x is calculated this way:
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; address = scheduler_global_thread + scheduler_global_length * x + scheduler_offset_stackp
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;
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;; scheduler memory map
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;
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; $060 active thread
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; $061 number of threads
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; $062 sr1 of scheduler
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; $063 sr2 of scheduler
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; // we still have 8 bytes of memory here
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; $06B
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; thread 0
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; $06B internal sr
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; $06C iph
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; $06D ipl
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; $06E sr
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; $06F sph
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; $070 spl
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; $071
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; gpr
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; $090
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; $090
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; $091
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; thread 1
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; $091 internal sr
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; $092 iph
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; $093 ipl
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; $094 sr
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; $095 sph
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; $096 spl
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; $097
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; gpr
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; $0B6
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; $0B6
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; $0B7
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; thread 2
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; $0B7 internal sr
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; $0B8 iph
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; $0B9 ipl
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; $0BA sr
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; $0BB sph
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; $0BC spl
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; $0BD
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; gpr
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; $0DC
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; $0DC
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; $0DD
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; thread 3
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; $0DD internal sr
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; $0DE iph
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; $0DF ipl
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; $0E0 sr
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; $0E1 sph
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; $0E2 spl
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; $0E3
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; gpr
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; $102
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; $102
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;
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;
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;; stacks
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;
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; As we should support 5 threads, we need 5 stacks.
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; For the calculation of the stack space (see global memory map) I assumed that
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; no stack will grow over 127 entries.
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; Our initial stackpointer for thread x will be calculated this way:
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; address = schedulder_global_stacks + scheduler_offset_stacks * x
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;
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;;
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SchedulerInit:
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push r10
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in r10, sreg
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push r10
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push r11
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push xl
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push xh
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; first we'll clear all scheduler memory cells
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ldi r10, 0
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ldi r11, low (scheduler_global_lastad)
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ldi xl, low (scheduler_global_active)
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ldi xh, high(scheduler_global_active)
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SchedulerInitLoop1: ; while(xl++ != r11)
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st x+, r10
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cp xl, r11
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brne SchedulerInitLoop1
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; add main-thread
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call SchedulerAddThread
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; start scheduler timer
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; we will use timer0 because we don't use all posibilities of timer2
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; TODO
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pop xh
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pop xl
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pop r11
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pop r10
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out sreg, r10
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pop r10
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ret
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SchedulerAddThread:
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ret
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SchedulerChangeThread:
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; puh, that will get hard
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; first we have to get the current instruction pointer
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push xl
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push xh
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push r16
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in r16, sreg
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ldi xl, low (scheduler_global_unused)
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ldi xh, high(scheduler_global_unused)
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st x+, r16 ; sreg is on unused[0]
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pop r16
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st x+, r16 ; r16 is on unused[1]
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pop r16
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st x+, r16 ; xh is on unused[2]
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pop r16
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st x+, r16 ; xl is on unused[3]
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st x+, r17 ; r17 is on unused[4]
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st x+, r18 ; r18 is on unused[5]
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st x+, r19 ; r19 is on unused[6]
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st x+, r20 ; r19 is on unused[7]
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pop r16 ; epic win !!!!!111
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pop r17
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; instruction pointer high is now in r16; low in r17
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; next we have to determine where we have to store our data
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ldd r18 scheduler_global_active
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; number of current thread is now in r18
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; now we have to determine the start address of our thread memory
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ldi xl, low (scheduler_global_thread)
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ldi xh, high(scheduler_global_thread)
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ldi r19, scheduler_global_length
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ldi r20, 0
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SchedulerChangeThreadLoop1:
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cp r20, r18
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breq SchedulerChangeThreadLoop1End
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; we can do the following, because the address can not be greater
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; than 0x00FF (as you can see in the scheduler memory map)
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add xl, r19
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inc r20
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jmp SchedulerChangeThreadLoop1
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SchedulerChangeThreadLoop1End:
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; x now contains the start address of our thread memory
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; let's copy some data
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; this is, because we don't want to modify the status register
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ld r11, x+
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; instruction pointer
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st x+, r16
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st x+, r17
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; we need the status register, it's saved in unused[0]
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ldd r16, scheduler_global_unused
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st x+, r16
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; so: the next step is the stack pointer
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in r16, sph
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st x+, r16
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in r16, spl
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st x+, r16
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; whew. next we have to save all the pgrs
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st x+, r0
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st x+, r1
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st x+, r2
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st x+, r3
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st x+, r4
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st x+, r5
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st x+, r6
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st x+, r7
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st x+, r8
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st x+, r9
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st x+, r10
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st x+, r11
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st x+, r12
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st x+, r13
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st x+, r14
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st x+, r15
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ldd r16, (scheduler_global_unused + 1)
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st x+, r16
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ldd r16, (scheduler_global_unused + 4) ; this is r17
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st x+, r16
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ldd r16, (scheduler_global_unused + 5) ; this is r18
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st x+, r16
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ldd r16, (scheduler_global_unused + 6) ; this is r19
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st x+, r16
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ldd r16, (scheduler_global_unused + 7) ; this is r20
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st x+, r16
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st x+, r21
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st x+, r22
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st x+, r23
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st x+, r24
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st x+, r25
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ldd r16, (scheduler_global_unused + 3) ; this is xl
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st x+, r16
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ldd r16, (scheduler_global_unused + 2) ; this is xh
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st x+, r16
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st x+, yl
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st x+, yh
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st x+, zl
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st x+, zh
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; soooo. we now have to get to know which is the next thread.
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; TODO:
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; - (r18 contains the nr of the active thread)
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; - r17 = scheduler_global_number
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; - if r18 = r17 then r18 = 0 else r18++
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; - cache ip
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; - cache sr
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; - replace sp
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; - do the same game in the other direction :D
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;
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; I'll write that later.
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ret
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