source: buchla-68k/orig/MT/SMSIG.S@ a838f5b

Last change on this file since a838f5b was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 8 years ago

Imported original source code.
  • Property mode set to 100755
File size: 4.9 KB
Line 
1* ------------------------------------------------------------------------------
2* smsig.s -- Multi-Tasker -- SM_Sig and SM_Wait for assembly language routines
3* Version 22 -- 1988-04-17 -- D.N. Lynx Crowe
4* (c) Copyright 1988 -- D.N. Lynx Crowe
5* ------------------------------------------------------------------------------
6*
7 .text
8*
9 .xdef SM_Sig
10 .xdef SM_Wait
11*
12 .xref _MT_RdyQ
13 .xref _MT_CurP
14*
15 .xref _MT_LSpc
16 .xref _MT_LWpc
17*
18* Register equates
19* ----------------
20RSEM .equ D7 * semaphore contents
21RIPL .equ D6 * saved IPL
22RPRI .equ D5 * task priority
23RTMP .equ D4 * temporary
24*
25RTCP .equ A5 * TCB pointer
26RPRV .equ A4 * previous TCB pointer
27RCUR .equ A3 * current TCB pointer
28RPTR .equ A2 * temporary TCB pointer
29*
30* Miscellaneous equates
31* ---------------------
32IPL7 .equ $0700 * processor IPL 7 mask
33TRAP_NXT .equ 9 * swapper TRAP number 2
34STP_BIT .equ 3 * stop bit number (LS byte of flags)
35*
36* Parameter offsets
37* -----------------
38PSEM .equ 8 * LONG -- pointer to semaphore
39*
40 .page
41*
42* TCB definitions
43* ---------------
44NEXT .equ 0 * LONG - next TCB in queue
45FWD .equ NEXT+4 * LONG - next TCB in chain
46TID .equ FWD+4 * WORD - task ID
47PRI .equ TID+2 * WORD - task priority
48SLICE .equ PRI+2 * LONG - slice time limit
49TCB_REG .equ SLICE+4 * LONG[16] - registers
50TCB_SP .equ TCB_REG+64 * LONG - stack pointer
51TCB_PC .equ TCB_SP+4 * LONG - program counter
52TCB_SR .equ TCB_PC+4 * WORD - status register
53FLAGS .equ TCB_SR+2 * WORD - task flags
54TOS .equ FLAGS+2 * LONG - top of stack pointer
55*
56MTF_RDY .equ $0001 * 'ready' bit
57*
58MTF_SWT .equ $0002 * 'wait' bit
59NOT_SWT .equ $FFFD * 'wait' bit complement
60*
61 .page
62*
63* SM_Sig -- signal a semaphore
64* ------ ------------------
65SM_Sig: link a6,#0 * link stack frames
66 move.l 4(a6),_MT_LSpc * log last PC
67 movem.l RTMP-RSEM/RPTR-RTCP,-(sp) * save registers
68 move.w sr,RIPL * save interrupt level
69 ori.w #IPL7,sr * DISABLE INTERRUPTS
70 movea.l PSEM(a6),RPTR * get pointer to semaphore
71*
72L00: move.l (RPTR),RSEM * get semaphore contents
73 beq L13 * jump if empty
74*
75 btst #0,RSEM * check for waiting tasks
76 beq L10 * jump if something waiting
77*
78 move.l RSEM,RTMP * check for maximum count
79 andi.l #$FFFFFFFE,RTMP * ...
80 cmpi.l #$FFFFFFFE,RTMP * ...
81 beq L9 * jump if limit hit
82*
83 addq.l #2,RSEM * add 1 to semaphore count
84 bra L12 * go update semaphore
85*
86L10: movea.l RSEM,RTCP * point at waiting task TCB
87 move.l (RTCP),RSEM * update semaphore
88 clr.l (RTCP) * clear NEXT of TCB
89 andi.w #NOT_SWT,FLAGS(RTCP) * turn off TCB wait bit
90 btst.b #STP_BIT,FLAGS+1(RTCP) * check stop bit
91 beq L01 * jump if not set
92*
93 bclr.b #STP_BIT,FLAGS+1(RTCP) * clear stop bit
94 bra L00 * go check for another task
95*
96L01: move.w PRI(RTCP),RPRI * setup to put TCB on ready queue
97 lea _MT_RdyQ,RCUR * ...
98*
99L15: movea.l RCUR,RPRV * follow TCB chain
100 movea.l (RPRV),RCUR * ...
101 move.l RCUR,RTMP * ...
102 beq L14 * jump if end of chain
103*
104 cmp.w PRI(RCUR),RPRI * is this the place ?
105 bls L15 * loop to next one if not
106*
107L14: move.l RTCP,(RPRV) * put TCB on ready queue
108 move.l RCUR,(RTCP) * ...
109 ori.w #MTF_RDY,FLAGS(RTCP) * set TCB ready bit
110 bra L12
111*
112L13: moveq.l #3,RSEM * set semaphore count = 1
113*
114L12: move.l RSEM,(RPTR) * update semaphore
115*
116L9: move.w RIPL,sr * RESTORE INTERRUPTS
117 movem.l (sp)+,RTMP-RSEM/RPTR-RTCP * restore registers
118 unlk a6 * unlink stack frames
119 rts
120*
121 .page
122*
123* SM_Wait -- wait on a semaphore
124* ------- -------------------
125SM_Wait: link a6,#0 * link stack frames
126 move.l 4(a6),_MT_LWpc * log last PC
127 movem.l RTMP-RSEM/RPTR-RCUR,-(sp) * save registers
128 move.w sr,RIPL * save interrupt level
129 ori.w #IPL7,sr * DISABLE INTERRUPTS
130 movea.l PSEM(a6),RPTR * get semaphore pointer
131 move.l (RPTR),RSEM * get semaphore contents
132 beq L19 * jump if not signalled yet
133*
134 btst.l #0,RSEM * see if anything is waiting
135 beq L19 * jump if so
136*
137 move.l RSEM,RTMP * check semaphore count
138 andi.l #$FFFFFFFE,RTMP * ...
139 beq L20 * jump if not signalled yet
140*
141 subq.l #2,RSEM * decrement semaphore count
142 move.l RSEM,(RPTR) * update semaphore
143 bra L18 * exit
144*
145L20: clr.l (RPTR) * make SEM a NIL pointer
146*
147L19: movea.l _MT_CurP,RCUR * point at current TCB
148 clr.l (RCUR) * clear NEXT of current TCB
149 ori.w #MTF_SWT,FLAGS(RCUR) * indicate we're waiting
150*
151L30: tst.l (RPTR) * pointing at SEM queue end ?
152 beq L31 * jump if so
153*
154 movea.l (RPTR),RPTR * point at next TCB in SEM queue
155 bra L30 * keep searching for end of queue
156*
157L31: move.l RCUR,(RPTR) * set NEXT of end of queue
158 trap #TRAP_NXT * swap to next ready task
159*
160L18: move.w RIPL,sr * RESTORE INTERRUPTS
161 movem.l (sp)+,RTMP-RSEM/RPTR-RCUR * restore registers
162 unlk a6 * unlink stack frames
163 rts * return to caller
164*
165 .end
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