1 /* hp2100_pif.c: HP 12620A/12936A Privileged Interrupt Fence simulator
2
3 Copyright (c) 2008-2018, J. David Bryan
4
5 Permission is hereby granted, free of charge, to any person obtaining a
6 copy of this software and associated documentation files (the "Software"),
7 to deal in the Software without restriction, including without limitation
8 the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 and/or sell copies of the Software, and to permit persons to whom the
10 Software is furnished to do so, subject to the following conditions:
11
12 The above copyright notice and this permission notice shall be included in
13 all copies or substantial portions of the Software.
14
15 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
19 IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
20 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
21
22 Except as contained in this notice, the name of the author shall not be
23 used in advertising or otherwise to promote the sale, use or other dealings
24 in this Software without prior written authorization from the author.
25
26 PIF 12620A/12936A Privileged Interrupt Fence
27
28 11-Jun-18 JDB Revised I/O model
29 15-Mar-17 JDB Trace flags are now global
30 11-Mar-17 JDB Revised the trace outputs
31 17-Jan-17 JDB Changed "hp_---sc" and "hp_---dev" to "hp_---_dib"
32 13-May-16 JDB Modified for revised SCP API function parameter types
33 10-Feb-12 JDB Deprecated DEVNO in favor of SC
34 28-Mar-11 JDB Tidied up signal handling
35 26-Oct-10 JDB Changed I/O signal handler for revised signal model
36 26-Jun-08 JDB Rewrote device I/O to model backplane signals
37 18-Jun-08 JDB Created PIF device
38
39 References:
40 - 12620A Breadboard Interface Kit Operating and Service Manual
41 (12620-90001, May 1978)
42 - 12936A Privileged Interrupt Fence Accessory Installation and Service Manual
43 (12936-90001, March 1974)
44
45
46 The Privileged Interupt Fence (PIF) was used in DOS and RTE systems to
47 provide privileged interrupt capability. In non-privileged systems, DOS and
48 RTE vectored all interrupts though the Central Interrupt Control (CIC)
49 routine. Within CIC, the interrupt system was turned off, the interrupt was
50 categorized, the associated driver was identified and mapped into logical
51 memory (if necessary), and the driver entered to handle the device service.
52 When the driver exited, the interrupt system was turned on before returning
53 to the point of interruption in the user's program. In addition, the DOS and
54 RTE operating systems themselves executed with the interrupt system off, as
55 they were not reentrant.
56
57 This process proved too lengthy for certain devices, which would lose
58 interrupts or be forced to limit I/O speeds as a result. To allow faster
59 service, a driver could be written as a "privileged" driver and generated
60 into a privileged system. A privileged system operated with the interrupt
61 system on when handling unprivileged device interrupts or executing within
62 the operating system. The PIF card was installed in the I/O backplane to
63 separate privileged from unprivileged devices by controlling the interrupt
64 priority chain signal (PRL) to lower-priority devices. The privileged cards
65 located below the fence were allowed to interrupt the service routines of the
66 unprivileged cards that were located above the fence.
67
68 When an unprivileged device interrupted, CIC would be entered as usual, and
69 the interrupt system would be turned off. However, after the system state
70 was saved, the PIF would be configured to break the priority chain (deny
71 PRL), so that subsequent interrupts from all unprivileged devices would be
72 deferred. Then the interrupt system would be turned on before normal CIC
73 processing continued. Interrupts from additional unprivileged devices would
74 be held off by the PIF until the driver completed and CIC returned, just as
75 in a non-privileged system.
76
77 However, if a privileged device interrupted, the interrupt would be allowed,
78 because the interrupt system was on, and the priority chain was intact for
79 the devices below the fence. A privileged device bypassed CIC and entered
80 the associated device driver directly, and this would occur even if an
81 unprivileged device driver or the operating system itself were executing.
82 This provided very fast interrupt service time.
83
84 HP produced two PIF cards: the 12936A Privileged Interrupt Fence Accessory
85 for DOS, and the 12620A Breadboard Interface for RTE. They behaved quite
86 differently and were not interchangeable.
87
88 The 12620A had the standard control and flag circuitry. It behaved as most
89 cards did; setting control and flag together lowered PRL and generated an
90 interrupt. The control and flag flip-flops were set and cleared with STC/CLC
91 and STF/CLF instructions. The SFS/SFC instructions could be used to test the
92 flag state.
93
94 The 12936A had a unique behavior. Setting either control or flag lowered
95 PRL. An interrupt occurred when flag was set and control was clear. The
96 control flip-flop was controlled with STC/CLC. The flag flip-flop was set
97 with OTA/B and cleared with CLF. SFC and SFS were not implemented and never
98 skipped.
99 */
100
101
102
103 #include "hp2100_defs.h"
104 #include "hp2100_io.h"
105
106
107
108 /* Device flags */
109
110 #define DEV_V_12936 (DEV_V_UF + 0) /* 12936A card */
111
112 #define DEV_12936 (1 << DEV_V_12936)
113
114
115 /* Interface state */
116
117 typedef struct {
118 FLIP_FLOP control; /* control flip-flop */
119 FLIP_FLOP flag; /* flag flip-flop */
120 FLIP_FLOP flag_buffer; /* flag buffer flip-flop */
121 } CARD_STATE;
122
123 static CARD_STATE pif; /* per-card state */
124
125
126 /* Interface local SCP support routines */
127
128 static INTERFACE pif_interface;
129
130
131 /* Interface local SCP support routines */
132
133 static t_stat pif_reset (DEVICE *dptr);
134 static t_stat pif_set_card (UNIT *uptr, int32 val, char *cptr, void *desc);
135 static t_stat pif_show_card (FILE *st, UNIT *uptr, int32 val, void *desc);
136
137
138 /* Interface SCP data structures */
139
140
141 /* Device information block */
142
143 static DIB pif_dib = {
144 &pif_interface, /* the device's I/O interface function pointer */
145 PIF, /* the device's select code (02-77) */
146 0, /* the card index */
147 "12620A/12936A Privileged Interrupt Fence", /* the card description */
148 NULL /* the ROM description */
149 };
150
151
152 /* Unit list.
153
154
155 Implementation notes:
156
157 1. The SIMH developer's manual says that a device's unit list may be NULL.
158 However, if this is done, the register state cannot be examined or
159 altered via SCP. To work around this problem, we define a dummy unit
160 that is not used otherwise.
161 */
162
163 static UNIT pif_unit [] = {
164 { UDATA (NULL, 0, 0) }
165 };
166
167
168 /* Register list */
169
170 static REG pif_reg [] = {
171 /* Macro Name Location Offset */
172 /* ------ ------ ------------------- ------ */
173 { FLDATA (CTL, pif.control, 0) },
174 { FLDATA (FLG, pif.flag, 0) },
175 { FLDATA (FBF, pif.flag_buffer, 0) },
176
177 DIB_REGS (pif_dib),
178
179 { NULL }
180 };
181
182
183 /* Modifier list */
184
185 static MTAB pif_mod [] = {
186 /* Entry Flags Value Print String Match String Validation Display Descriptor */
187 /* ------------------- ----- ------------ ------------ -------------- -------------- ----------------- */
188 { MTAB_XDV, 0, NULL, "12620A", &pif_set_card, NULL, NULL },
189 { MTAB_XDV, 1, NULL, "12936A", &pif_set_card, NULL, NULL },
190 { MTAB_XDV, 0, "TYPE", NULL, NULL, &pif_show_card, NULL },
191
192 { MTAB_XDV, 1u, "SC", "SC", &hp_set_dib, &hp_show_dib, (void *) &pif_dib },
193 { MTAB_XDV | MTAB_NMO, ~1u, "DEVNO", "DEVNO", &hp_set_dib, &hp_show_dib, (void *) &pif_dib },
194 { 0 }
195 };
196
197
198 /* Debugging trace list */
199
200 static DEBTAB pif_deb [] = {
201 { "CMD", TRACE_CMD }, /* interface commands */
202 { "IOBUS", TRACE_IOBUS }, /* interface I/O bus signals and data words */
203 { NULL, 0 }
204 };
205
206
207 /* Device descriptor */
208
209 DEVICE pif_dev = {
210 "PIF", /* device name */
211 pif_unit, /* unit array */
212 pif_reg, /* register array */
213 pif_mod, /* modifier array */
214 1, /* number of units */
215 10, /* address radix */
216 31, /* address width */
217 1, /* address increment */
218 8, /* data radix */
219 8, /* data width */
220 NULL, /* examine routine */
221 NULL, /* deposit routine */
222 &pif_reset, /* reset routine */
223 NULL, /* boot routine */
224 NULL, /* attach routine */
225 NULL, /* detach routine */
226 &pif_dib, /* device information block */
227 DEV_DISABLE | DEV_DEBUG, /* device flags */
228 0, /* debug control flags */
229 pif_deb, /* debug flag name table */
230 NULL, /* memory size change routine */
231 NULL }; /* logical device name */
232
233
234
235 /* Interface local SCP support routines */
236
237
238
239 /* Privileged interrupt fence interface.
240
241 Operation of the 12620A and the 12936A is different. The I/O responses of
242 the two cards are summarized below:
243
244 Signal 12620A Action 12936A Action
245 ------ -------------------- --------------------
246 POPIO Set FBF, FLG Clear FBF, FLG
247 CRS Clear CTL Clear CTL
248 CLC Clear CTL Clear CTL
249 STC Set CTL Set CTL
250 CLF Clear FBF, FLG Clear FBF, FLG
251 STF Set FBF, FLG none
252 SFC Skip if FLG clear none
253 SFS Skip if FLG set none
254 IOI none none
255 IOO none Set FBF, FLG
256 PRL ~(CTL * FLG) ~(CTL + FLG)
257 IRQ CTL * FLG * FBF ~CTL * FLG * FBF
258 IAK Clear FBF Clear FBF
259 SRQ Follows FLG Not driven
260
261 Note that PRL and IRQ are non-standard for the 12936A.
262 */
263
pif_interface(const DIB * dibptr,INBOUND_SET inbound_signals,HP_WORD inbound_value)264 static SIGNALS_VALUE pif_interface (const DIB *dibptr, INBOUND_SET inbound_signals, HP_WORD inbound_value)
265 {
266 const t_bool is_rte_pif = (pif_dev.flags & DEV_12936) == 0; /* TRUE if 12620A card */
267 INBOUND_SIGNAL signal;
268 INBOUND_SET working_set = inbound_signals;
269 SIGNALS_VALUE outbound = { ioNONE, 0 };
270 t_bool irq_enabled = FALSE;
271
272 while (working_set) {
273 signal = IONEXTSIG (working_set); /* isolate the next signal */
274
275 switch (signal) { /* dispatch I/O signal */
276
277 case ioCLF: /* clear flag flip-flop */
278 pif.flag_buffer = CLEAR; /* clear flag buffer and flag */
279 pif.flag = CLEAR;
280 break;
281
282
283 case ioSTF: /* set flag flip-flop */
284 if (is_rte_pif) /* RTE PIF? */
285 pif.flag_buffer = SET; /* set flag buffer */
286 break;
287
288
289 case ioENF: /* enable flag */
290 if (pif.flag_buffer == SET) /* if the flag buffer flip-flop is set */
291 pif.flag = SET; /* then set the flag flip-flop */
292 break;
293
294
295 case ioSFC: /* skip if flag is clear */
296 if (is_rte_pif && pif.flag == CLEAR) /* only the 12620A card */
297 outbound.signals |= ioSKF; /* responds to SFC */
298 break;
299
300
301 case ioSFS: /* skip if flag is set */
302 if (is_rte_pif && pif.flag == SET) /* only the 12620A card */
303 outbound.signals |= ioSKF; /* responds to SFS */
304 break;
305
306
307 case ioIOO: /* I/O data output */
308 if (is_rte_pif == FALSE) { /* DOS PIF? */
309 pif.flag_buffer = SET; /* set flag buffer */
310 working_set |= ioENF | ioSIR; /* set ENF and SIR (not normally done for IOO) */
311 }
312 break;
313
314
315 case ioPOPIO: /* power-on preset to I/O */
316 if (is_rte_pif)
317 pif.flag_buffer = SET;
318
319 else {
320 pif.flag_buffer = CLEAR;
321 pif.flag = CLEAR;
322 }
323
324 tprintf (pif_dev, TRACE_CMD, "Power-on reset\n");
325 break;
326
327
328 case ioCRS: /* control reset */
329 pif.control = CLEAR; /* clear control */
330 tprintf (pif_dev, TRACE_CMD, "Control reset\n");
331 break;
332
333
334 case ioCLC: /* clear control flip-flop */
335 pif.control = CLEAR; /* clear control */
336 break;
337
338
339 case ioSTC: /* set control flip-flop */
340 pif.control = SET; /* set control */
341 break;
342
343
344 case ioSIR: /* set interrupt request */
345 if (is_rte_pif & pif.control & pif.flag /* if control and flag are set (12620A) */
346 || !is_rte_pif & (pif.control | pif.flag)) /* or control or flag are clear (12936A) */
347 outbound.signals |= cnVALID; /* then deny PRL */
348 else /* otherwise */
349 outbound.signals |= cnPRL | cnVALID; /* conditionally assert PRL */
350
351 if (~(is_rte_pif ^ pif.control) /* if control is set (12620A) or clear (12936A) */
352 & pif.flag & pif.flag_buffer) /* and flag and flag buffer are set */
353 outbound.signals |= cnIRQ | cnVALID; /* then conditionally assert IRQ */
354
355 if (is_rte_pif && pif.flag == SET) /* if 12620A and flag is set */
356 outbound.signals |= ioSRQ; /* then assert SRQ */
357
358 tprintf (pif_dev, TRACE_CMD, "Fence %s%s lower-priority interrupts\n",
359 (outbound.signals & cnIRQ ? "requests an interrupt and " : ""),
360 (outbound.signals & cnPRL ? "allows" : "inhibits"));
361 break;
362
363
364 case ioIAK: /* interrupt acknowledge */
365 pif.flag_buffer = CLEAR;
366 break;
367
368
369 case ioIEN: /* interrupt enable */
370 irq_enabled = TRUE;
371 break;
372
373
374 case ioPRH: /* priority high */
375 if (irq_enabled && outbound.signals & cnIRQ) /* if IRQ is enabled and conditionally asserted */
376 outbound.signals |= ioIRQ | ioFLG; /* then assert IRQ and FLG */
377
378 if (!irq_enabled || outbound.signals & cnPRL) /* if IRQ is disabled or PRL is conditionally asserted */
379 outbound.signals |= ioPRL; /* then assert it unconditionally */
380 break;
381
382
383 case ioIOI: /* not used by this interface */
384 case ioEDT: /* not used by this interface */
385 case ioPON: /* not used by this interface */
386 break;
387 }
388
389 IOCLEARSIG (working_set, signal); /* remove the current signal from the set */
390 }
391
392 return outbound; /* return the outbound signals and value */
393 }
394
395
396 /* Simulator reset routine */
397
pif_reset(DEVICE * dptr)398 static t_stat pif_reset (DEVICE *dptr)
399 {
400 io_assert (dptr, ioa_POPIO); /* PRESET the device */
401 return SCPE_OK;
402 }
403
404
405
406 /* Privileged interrupt fence local utility routines */
407
408
409 /* Set card type.
410
411 val == 0 --> set to 12936A (DOS PIF)
412 val == 1 --> set to 12620A (RTE PIF)
413 */
414
pif_set_card(UNIT * uptr,int32 val,char * cptr,void * desc)415 static t_stat pif_set_card (UNIT *uptr, int32 val, char *cptr, void *desc)
416 {
417 if ((val < 0) || (val > 1) || (cptr != NULL)) /* sanity check */
418 return SCPE_ARG; /* bad argument */
419
420 if (val) /* DOS PIF selected? */
421 pif_dev.flags = pif_dev.flags | DEV_12936; /* set to 12936A */
422 else /* RTE PIF selected */
423 pif_dev.flags = pif_dev.flags & ~DEV_12936; /* set to 12620A */
424
425 return SCPE_OK;
426 }
427
428
429 /* Show card type */
430
pif_show_card(FILE * st,UNIT * uptr,int32 val,void * desc)431 static t_stat pif_show_card (FILE *st, UNIT *uptr, int32 val, void *desc)
432 {
433 if (pif_dev.flags & DEV_12936)
434 fputs ("12936A", st);
435 else
436 fputs ("12620A", st);
437
438 return SCPE_OK;
439 }
440