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/* pdp1_cpu.c: PDP-1 CPU simulator
Copyright (c) 1993-2006, Robert M. Supnik
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
ROBERT M SUPNIK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of Robert M Supnik shall not be
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from Robert M Supnik.
cpu PDP-1 central processor
28-Jun-06 RMS Fixed bugs in MUS and DIV
22-Sep-05 RMS Fixed declarations (from Sterling Garwood)
16-Aug-05 RMS Fixed C++ declaration and cast problems
09-Nov-04 RMS Added instruction history
07-Sep-03 RMS Added additional explanation on I/O simulation
01-Sep-03 RMS Added address switches for hardware readin
23-Jul-03 RMS Revised to detect I/O wait hang
05-Dec-02 RMS Added drum support
06-Oct-02 RMS Revised for V2.10
20-Aug-02 RMS Added DECtape support
30-Dec-01 RMS Added old PC queue
07-Dec-01 RMS Revised to use breakpoint package
30-Nov-01 RMS Added extended SET/SHOW support
16-Dec-00 RMS Fixed bug in XCT address calculation
14-Apr-99 RMS Changed t_addr to unsigned
The PDP-1 was Digital's first computer. Although Digital built four
other 18b computers, the later systems (the PDP-4, PDP-7, PDP-9, and
PDP-15) were similar to each other and quite different from the PDP-1.
Accordingly, the PDP-1 requires a distinct simulator.
The register state for the PDP-1 is:
AC<0:17> accumulator
IO<0:17> IO register
OV overflow flag
PC<0:15> program counter
IOSTA I/O status register
SBS<0:2> sequence break flip flops
IOH I/O halt flip flop
IOS I/O syncronizer (completion) flip flop
EXTM extend mode
PF<1:6> program flags
SS<1:6> sense switches
TW<0:17> test word (switch register)
Questions:
cks: which bits are line printer print done and space done?
cks: is there a bit for sequence break enabled (yes, according
to the 1963 Handbook)
sbs: do sequence breaks accumulate while the system is disabled
(yes, according to the Maintenance Manual)
The PDP-1 has six instruction formats: memory reference, skips,
shifts, load immediate, I/O transfer, and operate. The memory
reference format is:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| op |in| address | memory reference
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
<0:4> <5> mnemonic action
00
02 AND AC = AC & M[MA]
04 IOR AC = AC | M[MA]
06 XOR AC = AC ^ M[MA]
10 XCT M[MA] is executed as an instruction
12
14
16 0 CAL M[100] = AC, AC = PC, PC = 101
16 1 JDA M[MA] = AC, AC = PC, PC = MA + 1
20 LAC AC = M[MA]
22 LIO IO = M[MA]
24 DAC M[MA] = AC
26 DAP M[MA]<6:17> = AC<6:17>
30 DIP M[MA]<0:5> = AC<0:5>
32 DIO M[MA] = IO
34 DZM M[MA] = 0
36
40 ADD AC = AC + M[MA]
42 SUB AC = AC - M[MA]
44 IDX AC = M[MA] = M[MA] + 1
46 ISP AC = M[MA] = M[MA] + 1, skip if AC >= 0
50 SAD skip if AC != M[MA]
52 SAS skip if AC == M[MA]
54 MUL AC'IO = AC * M[MA]
56 DIV AC, IO = AC'IO / M[MA]
60 JMP PC = MA
62 JSP AC = PC, PC = MA
Memory reference instructions can access an address space of 64K words.
The address space is divided into sixteen 4K word fields. An
instruction can directly address, via its 12b address, the entire
current field. If extend mode is off, indirect addresses access
the current field, and indirect addressing is multi-level; if off,
they can access all 64K, and indirect addressing is single level.
The skip format is:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1 0 1 0| | | | | | | | | | | | | | skip
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | \______/ \______/
| | | | | | | |
| | | | | | | +---- program flags
| | | | | | +------------- sense switches
| | | | | +------------------- AC == 0
| | | | +---------------------- AC >= 0
| | | +------------------------- AC < 0
| | +---------------------------- OV == 0
| +------------------------------- IO >= 0
+------------------------------------- invert skip
The shift format is:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1 0 1 1| subopcode | encoded count | shift
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
The load immediate format is:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1 1 0 0| S| immediate | LAW
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
<0:4> mnemonic action
70 LAW if S = 0, AC = IR<6:17>
else AC = ~IR<6:17>
The I/O transfer format is:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1 1 0 1| W| C| subopcode | device | I/O transfer
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
The IO transfer instruction sends the the specified subopcode to
specified I/O device. The I/O device may take data from the IO or
return data to the IO, initiate or cancel operations, etc. The
W bit specifies whether the CPU waits for completion, the C bit
whether a completion pulse will be returned from the device.
The operate format is:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 1 1 1 1 1| | | | | | | | | | | | | | operate
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | | \______/
| | | | | | | |
| | | | | | | +---- PF select
| | | | | | +---------- clear/set PF
| | | | | +------------------- or PC
| | | | +---------------------- clear AC
| | | +------------------------- halt
| | +---------------------------- CMA
| +------------------------------- or TW
+---------------------------------- clear IO
The operate instruction can be microprogrammed.
This routine is the instruction decode routine for the PDP-1.
It is called from the simulator control program to execute
instructions in simulated memory, starting at the simulated PC.
It runs until 'reason' is set non-zero.
General notes:
1. Reasons to stop. The simulator can be stopped by:
HALT instruction
breakpoint encountered
unimplemented instruction and STOP_INST flag set
XCT loop
indirect address loop
infinite wait state
I/O error in I/O simulator
2. Interrupts. With a single channel sequence break system, the
PDP-1 has a single break request (flop b2, here sbs<SB_V_RQ>).
If sequence breaks are enabled (flop sbm, here sbs<SB_V_ON>),
and one is not already in progress (flop b4, here sbs<SB_V_IP>),
a sequence break occurs.
3. Arithmetic. The PDP-1 is a 1's complement system. In 1's
complement arithmetic, a negative number is represented by the
complement (XOR 0777777) of its absolute value. Addition of 1's
complement numbers requires propagating the carry out of the high
order bit back to the low order bit.
4. Adding I/O devices. Three modules must be modified:
pdp1_defs.h add interrupt request definition
pdp1_cpu.c add IOT dispatch code
pdp1_sys.c add sim_devices table entry
*/
#include "pdp1_defs.h"
#define PCQ_SIZE 64 /* must be 2**n */
#define PCQ_MASK (PCQ_SIZE - 1)
#define PCQ_ENTRY pcq[pcq_p = (pcq_p - 1) & PCQ_MASK] = PC
#define UNIT_V_MDV (UNIT_V_UF + 0) /* mul/div */
#define UNIT_V_MSIZE (UNIT_V_UF + 1) /* dummy mask */
#define UNIT_MDV (1 << UNIT_V_MDV)
#define UNIT_MSIZE (1 << UNIT_V_MSIZE)
#define HIST_PC 0x40000000
#define HIST_V_SHF 18
#define HIST_MIN 64
#define HIST_MAX 65536
typedef struct {
uint32 pc;
uint32 ir;
uint32 ovac;
uint32 pfio;
uint32 ea;
uint32 opnd;
} InstHistory;
int32 M[MAXMEMSIZE] = { 0 }; /* memory */
int32 AC = 0; /* AC */
int32 IO = 0; /* IO */
int32 PC = 0; /* PC */
int32 OV = 0; /* overflow */
int32 SS = 0; /* sense switches */
int32 PF = 0; /* program flags */
int32 TA = 0; /* address switches */
int32 TW = 0; /* test word */
int32 iosta = 0; /* status reg */
int32 sbs = 0; /* sequence break */
int32 sbs_init = 0; /* seq break startup */
int32 ioh = 0; /* I/O halt */
int32 ios = 0; /* I/O syncronizer */
int32 cpls = 0; /* pending completions */
int32 extm = 0; /* ext mem mode */
int32 extm_init = 0; /* ext mem startup */
int32 stop_inst = 0; /* stop on rsrv inst */
int32 xct_max = 16; /* nested XCT limit */
int32 ind_max = 16; /* nested ind limit */
uint16 pcq[PCQ_SIZE] = { 0 }; /* PC queue */
int32 pcq_p = 0; /* PC queue ptr */
REG *pcq_r = NULL; /* PC queue reg ptr */
int32 hst_p = 0; /* history pointer */
int32 hst_lnt = 0; /* history length */
InstHistory *hst = NULL; /* instruction history */
extern UNIT *sim_clock_queue;
extern int32 sim_int_char;
extern uint32 sim_brk_types, sim_brk_dflt, sim_brk_summ; /* breakpoint info */
t_stat cpu_ex (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw);
t_stat cpu_dep (t_value val, t_addr addr, UNIT *uptr, int32 sw);
t_stat cpu_reset (DEVICE *dptr);
t_stat cpu_set_size (UNIT *uptr, int32 val, char *cptr, void *desc);
t_stat cpu_set_hist (UNIT *uptr, int32 val, char *cptr, void *desc);
t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, void *desc);
extern int32 ptr (int32 inst, int32 dev, int32 dat);
extern int32 ptp (int32 inst, int32 dev, int32 dat);
extern int32 tti (int32 inst, int32 dev, int32 dat);
extern int32 tto (int32 inst, int32 dev, int32 dat);
extern int32 lpt (int32 inst, int32 dev, int32 dat);
extern int32 dt (int32 inst, int32 dev, int32 dat);
extern int32 drm (int32 inst, int32 dev, int32 dat);
int32 sc_map[512] = {
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, /* 00000xxxx */
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, /* 00001xxxx */
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, /* 00010xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 00011xxxx */
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, /* 00100xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 00101xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 00110xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 00111xxxx */
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, /* 01000xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 01001xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 01010xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 01011xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 01100xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 01101xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 01110xxxx */
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, /* 01111xxxx */
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, /* 10000xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 10001xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 10010xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 10011xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 10100xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 10101xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 10110xxxx */
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, /* 11011xxxx */
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, /* 11000xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 11001xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 11010xxxx */
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, /* 11011xxxx */
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, /* 11100xxxx */
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, /* 11101xxxx */
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, /* 11110xxxx */
5, 6, 6, 7, 6, 7, 7, 8, 6, 7, 7, 8, 7, 8, 8, 9 /* 11111xxxx */
};
/* CPU data structures
cpu_dev CPU device descriptor
cpu_unit CPU unit
cpu_reg CPU register list
cpu_mod CPU modifier list
*/
UNIT cpu_unit = { UDATA (NULL, UNIT_FIX + UNIT_BINK, MAXMEMSIZE) };
REG cpu_reg[] = {
{ ORDATA (PC, PC, ASIZE) },
{ ORDATA (AC, AC, 18) },
{ ORDATA (IO, IO, 18) },
{ FLDATA (OV, OV, 0) },
{ ORDATA (PF, PF, 6) },
{ ORDATA (SS, SS, 6) },
{ ORDATA (TA, TA, ASIZE) },
{ ORDATA (TW, TW, 18) },
{ FLDATA (EXTM, extm, 0) },
{ ORDATA (IOSTA, iosta, 18), REG_RO },
{ FLDATA (SBON, sbs, SB_V_ON) },
{ FLDATA (SBRQ, sbs, SB_V_RQ) },
{ FLDATA (SBIP, sbs, SB_V_IP) },
{ FLDATA (IOH, ioh, 0) },
{ FLDATA (IOS, ios, 0) },
{ ORDATA (CPLS, cpls, 6) },
{ BRDATA (PCQ, pcq, 8, ASIZE, PCQ_SIZE), REG_RO+REG_CIRC },
{ ORDATA (PCQP, pcq_p, 6), REG_HRO },
{ FLDATA (STOP_INST, stop_inst, 0) },
{ FLDATA (SBS_INIT, sbs_init, SB_V_ON) },
{ FLDATA (EXTM_INIT, extm_init, 0) },
{ DRDATA (XCT_MAX, xct_max, 8), PV_LEFT + REG_NZ },
{ DRDATA (IND_MAX, ind_max, 8), PV_LEFT + REG_NZ },
{ ORDATA (WRU, sim_int_char, 8) },
{ NULL }
};
MTAB cpu_mod[] = {
{ UNIT_MDV, UNIT_MDV, "multiply/divide", "MDV", NULL },
{ UNIT_MDV, 0, "no multiply/divide", "NOMDV", NULL },
{ UNIT_MSIZE, 4096, NULL, "4K", &cpu_set_size },
{ UNIT_MSIZE, 8192, NULL, "8K", &cpu_set_size },
{ UNIT_MSIZE, 12288, NULL, "12K", &cpu_set_size },
{ UNIT_MSIZE, 16384, NULL, "16K", &cpu_set_size },
{ UNIT_MSIZE, 20480, NULL, "20K", &cpu_set_size },
{ UNIT_MSIZE, 24576, NULL, "24K", &cpu_set_size },
{ UNIT_MSIZE, 28672, NULL, "28K", &cpu_set_size },
{ UNIT_MSIZE, 32768, NULL, "32K", &cpu_set_size },
{ UNIT_MSIZE, 49152, NULL, "48K", &cpu_set_size },
{ UNIT_MSIZE, 65536, NULL, "64K", &cpu_set_size },
{ MTAB_XTD|MTAB_VDV|MTAB_NMO|MTAB_SHP, 0, "HISTORY", "HISTORY",
&cpu_set_hist, &cpu_show_hist },
{ 0 }
};
DEVICE cpu_dev = {
"CPU", &cpu_unit, cpu_reg, cpu_mod,
1, 8, ASIZE, 1, 8, 18,
&cpu_ex, &cpu_dep, &cpu_reset,
NULL, NULL, NULL,
NULL, 0
};
t_stat sim_instr (void)
{
extern int32 sim_interval;
int32 IR, MA, op, i, t, xct_count;
int32 sign, signd, v;
int32 dev, io_data, sc, skip;
t_stat reason;
static int32 fs_test[8] = {
0, 040, 020, 010, 04, 02, 01, 077
};
#define EPC_WORD ((OV << 17) | (extm << 16) | PC)
#define INCR_ADDR(x) (((x) & EPCMASK) | (((x) + 1) & DAMASK))
#define DECR_ADDR(x) (((x) & EPCMASK) | (((x) - 1) & DAMASK))
#define ABS(x) ((x) ^ (((x) & 0400000)? 0777777: 0))
/* Main instruction fetch/decode loop: check events and interrupts */
reason = 0;
while (reason == 0) { /* loop until halted */
if (sim_interval <= 0) { /* check clock queue */
if (reason = sim_process_event ()) break;
}
if (sbs == (SB_ON | SB_RQ)) { /* interrupt? */
sbs = SB_ON | SB_IP; /* set in prog flag */
PCQ_ENTRY; /* save old PC */
M[0] = AC; /* save state */
M[1] = EPC_WORD;
M[2] = IO;
PC = 3; /* fetch next from 3 */
extm = 0; /* extend off */
OV = 0; /* clear overflow */
}
if (sim_brk_summ && sim_brk_test (PC, SWMASK ('E'))) { /* breakpoint? */
reason = STOP_IBKPT; /* stop simulation */
break;
}
/* Fetch, decode instruction */
MA = PC; /* PC to MA */
IR = M[MA]; /* fetch instruction */
PC = INCR_ADDR (PC); /* increment PC */
xct_count = 0; /* track nested XCT's */
sim_interval = sim_interval - 1;
if (hst_lnt) { /* history enabled? */
hst_p = (hst_p + 1); /* next entry */
if (hst_p >= hst_lnt) hst_p = 0;
hst[hst_p].pc = MA | HIST_PC; /* save PC, IR, LAC, MQ */
hst[hst_p].ir = IR;
hst[hst_p].ovac = (OV << HIST_V_SHF) | AC;
hst[hst_p].pfio = (PF << HIST_V_SHF) | IO;
}
xct_instr: /* label for XCT */
if ((IR == (OP_JMP+IA+1)) && ((MA & EPCMASK) == 0) && (sbs & SB_ON)) {
sbs = sbs & ~SB_IP; /* seq debreak */
PCQ_ENTRY; /* save old PC */
OV = (M[1] >> 17) & 1; /* restore OV */
extm = (M[1] >> 16) & 1; /* restore ext mode */
PC = M[1] & AMASK; /* JMP I 1 */
continue;
}
op = ((IR >> 13) & 037); /* get opcode */
if ((op < 032) && (op != 007)) { /* mem ref instr */
MA = (MA & EPCMASK) | (IR & DAMASK); /* direct address */
if (IR & IA) { /* indirect addr? */
if (extm) MA = M[MA] & AMASK; /* if ext, one level */
else { /* multi-level */
for (i = 0; i < ind_max; i++) { /* count indirects */
t = M[MA]; /* get indirect word */
MA = (MA & EPCMASK) | (t & DAMASK);
if ((t & IA) == 0) break;
}
if (i >= ind_max) { /* indirect loop? */
reason = STOP_IND;
break;
}
} /* end else !extm */
} /* end if indirect */
if (hst_p) { /* history enabled? */
hst[hst_p].ea = MA;
hst[hst_p].opnd = M[MA];
}
}
switch (op) { /* decode IR<0:4> */
/* Logical, load, store instructions */
case 001: /* AND */
AC = AC & M[MA];
break;
case 002: /* IOR */
AC = AC | M[MA];
break;
case 003: /* XOR */
AC = AC ^ M[MA];
break;
case 004: /* XCT */
if (xct_count >= xct_max) { /* too many XCT's? */
reason = STOP_XCT;
break;
}
xct_count = xct_count + 1; /* count XCT's */
IR = M[MA]; /* get instruction */
goto xct_instr; /* go execute */
case 007: /* CAL, JDA */
MA = (PC & EPCMASK) | ((IR & IA)? (IR & DAMASK): 0100);
PCQ_ENTRY;
M[MA] = AC;
AC = EPC_WORD;
PC = INCR_ADDR (MA);
break;
case 010: /* LAC */
AC = M[MA];
break;
case 011: /* LIO */
IO = M[MA];
break;
case 012: /* DAC */
if (MEM_ADDR_OK (MA)) M[MA] = AC;
break;
case 013: /* DAP */
if (MEM_ADDR_OK (MA)) M[MA] = (AC & DAMASK) | (M[MA] & ~DAMASK);
break;
case 014: /* DIP */
if (MEM_ADDR_OK (MA)) M[MA] = (AC & ~DAMASK) | (M[MA] & DAMASK);
break;
case 015: /* DIO */
if (MEM_ADDR_OK (MA)) M[MA] = IO;
break;
case 016: /* DZM */
if (MEM_ADDR_OK (MA)) M[MA] = 0;
break;
/* Add, subtract, control
Add is performed in sequential steps, as follows:
1. add
2. end around carry propagate
3. overflow check
4. -0 cleanup
Subtract is performed in sequential steps, as follows:
1. complement AC
2. add
3. end around carry propagate
4. overflow check
5. complement AC
Because no -0 check is done, (-0) - (+0) yields a result of -0
*/
case 020: /* ADD */
t = AC;
AC = AC + M[MA];
if (AC > 0777777) AC = (AC + 1) & 0777777; /* end around carry */
if (((~t ^ M[MA]) & (t ^ AC)) & 0400000) OV = 1;
if (AC == 0777777) AC = 0; /* minus 0 cleanup */
break;
case 021: /* SUB */
t = AC ^ 0777777; /* complement AC */
AC = t + M[MA]; /* -AC + MB */
if (AC > 0777777) AC = (AC + 1) & 0777777; /* end around carry */
if (((~t ^ M[MA]) & (t ^ AC)) & 0400000) OV = 1;
AC = AC ^ 0777777; /* recomplement AC */
break;
case 022: /* IDX */
AC = M[MA] + 1;
if (AC >= 0777777) AC = (AC + 1) & 0777777;
if (MEM_ADDR_OK (MA)) M[MA] = AC;
break;
case 023: /* ISP */
AC = M[MA] + 1;
if (AC >= 0777777) AC = (AC + 1) & 0777777;
if (MEM_ADDR_OK (MA)) M[MA] = AC;
if (AC < 0400000) PC = INCR_ADDR (PC);
break;
case 024: /* SAD */
if (AC != M[MA]) PC = INCR_ADDR (PC);
break;
case 025: /* SAS */
if (AC == M[MA]) PC = INCR_ADDR (PC);
break;
case 030: /* JMP */
PCQ_ENTRY;
PC = MA;
break;
case 031: /* JSP */
AC = EPC_WORD;
PCQ_ENTRY;
PC = MA;
break;
case 034: /* LAW */
AC = (IR & 07777) ^ ((IR & IA)? 0777777: 0);
break;
/* Multiply and divide
Multiply and divide step and hardware multiply are exact implementations.
Hardware divide is a 2's complement analog to the actual hardware.
*/
case 026: /* MUL */
if (cpu_unit.flags & UNIT_MDV) { /* hardware? */
sign = AC ^ M[MA]; /* result sign */
IO = ABS (AC); /* IO = |AC| */
v = ABS (M[MA]); /* v = |mpy| */
for (i = AC = 0; i < 17; i++) {
if (IO & 1) AC = AC + v;
IO = (IO >> 1) | ((AC & 1) << 17);
AC = AC >> 1;
}
if ((sign & 0400000) && (AC | IO)) { /* negative, > 0? */
AC = AC ^ 0777777;
IO = IO ^ 0777777;
}
}
else { /* multiply step */
if (IO & 1) AC = AC + M[MA];
if (AC > 0777777) AC = (AC + 1) & 0777777;
// if (AC == 0777777) AC = 0;
IO = (IO >> 1) | ((AC & 1) << 17);
AC = AC >> 1;
}
break;
case 027: /* DIV */
if (cpu_unit.flags & UNIT_MDV) { /* hardware */
sign = AC ^ M[MA]; /* result sign */
signd = AC; /* remainder sign */
v = ABS (M[MA]); /* v = |divr| */
if (ABS (AC) >= v) break; /* overflow? */
if (AC & 0400000) {
AC = AC ^ 0777777; /* AC'IO = |AC'IO| */
IO = IO ^ 0777777;
}
for (i = t = 0; i < 18; i++) {
if (t) AC = (AC + v) & 0777777;
else AC = (AC - v) & 0777777;
t = AC >> 17;
if (i != 17) AC = ((AC << 1) | (IO >> 17)) & 0777777;
IO = ((IO << 1) | (t ^ 1)) & 0777777;
}
if (t) AC = (AC + v) & 0777777; /* correct remainder */
t = ((signd & 0400000) && AC)? AC ^ 0777777: AC;
AC = ((sign & 0400000) && IO)? IO ^ 0777777: IO;
IO = t;
PC = INCR_ADDR (PC); /* skip */
}
else { /* divide step */
t = AC >> 17;
AC = ((AC << 1) | (IO >> 17)) & 0777777;
IO = ((IO << 1) | (t ^ 1)) & 0777777;
if (IO & 1) AC = AC + (M[MA] ^ 0777777);
else AC = AC + M[MA] + 1;
if (AC > 0777777) AC = (AC + 1) & 0777777;
if (AC == 0777777) AC = 0;
}
break;
/* Skip and operate
Operates execute in the order shown; there are no timing conflicts
*/
case 032: /* skip */
v = (IR >> 3) & 07; /* sense switches */
t = IR & 07; /* program flags */
skip = (((IR & 02000) && (IO < 0400000)) || /* SPI */
((IR & 01000) && (OV == 0)) || /* SZO */
((IR & 00400) && (AC >= 0400000)) || /* SMA */
((IR & 00200) && (AC < 0400000)) || /* SPA */
((IR & 00100) && (AC == 0)) || /* SZA */
(v && ((SS & fs_test[v]) == 0)) || /* SZSn */
(t && ((PF & fs_test[t]) == 0))); /* SZFn */
if (IR & IA) skip = skip ^ 1; /* invert skip? */
if (skip) PC = INCR_ADDR (PC);
if (IR & 01000) OV = 0; /* SOV clears OV */
break;
case 037: /* operate */
if (IR & 04000) IO = 0; /* CLI */
if (IR & 00200) AC = 0; /* CLA */
if (IR & 02000) AC = AC | TW; /* LAT */
if (IR & 00100) AC = AC | EPC_WORD; /* LAP */
if (IR & 01000) AC = AC ^ 0777777; /* CMA */
if (IR & 00400) reason = STOP_HALT; /* HALT */
t = IR & 07; /* flag select */
if (IR & 010) PF = PF | fs_test[t]; /* STFn */
else PF = PF & ~fs_test[t]; /* CLFn */
break;
/* Shifts */
case 033:
sc = sc_map[IR & 0777]; /* map shift count */
switch ((IR >> 9) & 017) { /* case on IR<5:8> */
case 001: /* RAL */
AC = ((AC << sc) | (AC >> (18 - sc))) & 0777777;
break;
case 002: /* RIL */
IO = ((IO << sc) | (IO >> (18 - sc))) & 0777777;
break;
case 003: /* RCL */
t = AC;
AC = ((AC << sc) | (IO >> (18 - sc))) & 0777777;
IO = ((IO << sc) | (t >> (18 - sc))) & 0777777;
break;
case 005: /* SAL */
t = (AC & 0400000)? 0777777: 0;
AC = (AC & 0400000) | ((AC << sc) & 0377777) |
(t >> (18 - sc));
break;
case 006: /* SIL */
t = (IO & 0400000)? 0777777: 0;
IO = (IO & 0400000) | ((IO << sc) & 0377777) |
(t >> (18 - sc));
break;
case 007: /* SCL */
t = (AC & 0400000)? 0777777: 0;
AC = (AC & 0400000) | ((AC << sc) & 0377777) |
(IO >> (18 - sc));
IO = ((IO << sc) | (t >> (18 - sc))) & 0777777;
break;
case 011: /* RAR */
AC = ((AC >> sc) | (AC << (18 - sc))) & 0777777;
break;
case 012: /* RIR */
IO = ((IO >> sc) | (IO << (18 - sc))) & 0777777;
break;
case 013: /* RCR */
t = IO;
IO = ((IO >> sc) | (AC << (18 - sc))) & 0777777;
AC = ((AC >> sc) | (t << (18 - sc))) & 0777777;
break;
case 015: /* SAR */
t = (AC & 0400000)? 0777777: 0;
AC = ((AC >> sc) | (t << (18 - sc))) & 0777777;
break;
case 016: /* SIR */
t = (IO & 0400000)? 0777777: 0;
IO = ((IO >> sc) | (t << (18 - sc))) & 0777777;
break;
case 017: /* SCR */
t = (AC & 0400000)? 0777777: 0;
IO = ((IO >> sc) | (AC << (18 - sc))) & 0777777;
AC = ((AC >> sc) | (t << (18 - sc))) & 0777777;
break;
default: /* undefined */
reason = stop_inst;
break;
} /* end switch shifts */
break;
/* IOT - The simulator behaves functionally like a real PDP-1 but does not
use the same mechanisms or state bits. In particular,
- If an IOT does not specify IO_WAIT, the IOT will be executed, and the
I/O halt flag (IOH) will not be disturbed. On the real PDP-1, IOH is
stored in IHS, IOH is cleared, the IOT is executed, and then IOH is
restored from IHS. Because IHS is not otherwise used, it is not
explicitly simulated.
- If an IOT does specify IO_WAIT, then IOH specifies whether an I/O halt
(wait) is already in progress.
> If already set, I/O wait is in progress. The simulator looks for
a completion pulse (IOS). If there is a pulse, IOH is cleared. If
not, the IOT is fetched again. In either case, execution of the
IOT is skipped.
> If not set, I/O wait must start. IOH is set, the PC is backed up,
and the IOT is executed.
On a real PDP-1, IOC is the I/O command enable and enables the IOT
pulses. In the simulator, the enabling of IOT pulses is done through
code flow, and IOC is not explicitly simulated.
*/
case 035:
if (IR & IO_WAIT) { /* wait? */
if (ioh) { /* I/O halt? */
if (ios) ioh = 0; /* comp pulse? done */
else { /* wait more */
PC = DECR_ADDR (PC); /* re-execute */
if (cpls == 0) { /* any pending pulses? */
reason = STOP_WAIT; /* no, CPU hangs */
break;
}
sim_interval = 0; /* force event */
}
break; /* skip iot */
}
ioh = 1; /* turn on halt */
PC = DECR_ADDR (PC); /* re-execute */
}
dev = IR & 077; /* get dev addr */
io_data = IO; /* default data */
switch (dev) { /* case on dev */
case 000: /* I/O wait */
break;
case 001:
if (IR & 003700) io_data = dt (IR, dev, IO); /* DECtape */
else io_data = ptr (IR, dev, IO); /* paper tape rdr */
break;
case 002: case 030: /* paper tape rdr */
io_data = ptr (IR, dev, IO);
break;
case 003: /* typewriter */
io_data = tto (IR, dev, IO);
break;
case 004: /* keyboard */
io_data = tti (IR, dev, IO);
break;
case 005: case 006: /* paper tape punch */
io_data = ptp (IR, dev, IO);
break;
case 033: /* check status */
io_data = iosta | ((sbs & SB_ON)? IOS_SQB: 0);
break;
case 045: /* line printer */
io_data = lpt (IR, dev, IO);
break;
case 054: /* seq brk off */
sbs = sbs & ~SB_ON;
break;
case 055: /* seq brk on */
sbs = sbs | SB_ON;
break;
case 056: /* clear seq brk */
sbs = sbs & ~SB_IP;
break;
case 061: case 062: case 063: case 064: /* drum */
io_data = drm (IR, dev, IO);
break;
case 074: /* extend mode */
extm = (IR >> 11) & 1; /* set from IR<6> */
break;
default: /* undefined */
reason = stop_inst;
break;
} /* end switch dev */
IO = io_data & 0777777;
if (io_data & IOT_SKP) PC = INCR_ADDR (PC); /* skip? */
if (io_data >= IOT_REASON) reason = io_data >> IOT_V_REASON;
break;
default: /* undefined */
reason = STOP_RSRV; /* halt */
break;
} /* end switch opcode */
} /* end while */
pcq_r->qptr = pcq_p; /* update pc q ptr */
return reason;
}
/* Reset routine */
t_stat cpu_reset (DEVICE *dptr)
{
sbs = sbs_init;
extm = extm_init;
ioh = ios = cpls = 0;
OV = 0;
PF = 0;
pcq_r = find_reg ("PCQ", NULL, dptr);
if (pcq_r) pcq_r->qptr = 0;
else return SCPE_IERR;
sim_brk_types = sim_brk_dflt = SWMASK ('E');
return SCPE_OK;
}
/* Memory examine */
t_stat cpu_ex (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw)
{
if (addr >= MEMSIZE) return SCPE_NXM;
if (vptr != NULL) *vptr = M[addr] & 0777777;
return SCPE_OK;
}
/* Memory deposit */
t_stat cpu_dep (t_value val, t_addr addr, UNIT *uptr, int32 sw)
{
if (addr >= MEMSIZE) return SCPE_NXM;
M[addr] = val & 0777777;
return SCPE_OK;
}
/* Change memory size */
t_stat cpu_set_size (UNIT *uptr, int32 val, char *cptr, void *desc)
{
int32 mc = 0;
uint32 i;
if ((val <= 0) || (val > MAXMEMSIZE) || ((val & 07777) != 0))
return SCPE_ARG;
for (i = val; i < MEMSIZE; i++) mc = mc | M[i];
if ((mc != 0) && (!get_yn ("Really truncate memory [N]?", FALSE)))
return SCPE_OK;
MEMSIZE = val;
for (i = MEMSIZE; i < MAXMEMSIZE; i++) M[i] = 0;
return SCPE_OK;
}
/* Set history */
t_stat cpu_set_hist (UNIT *uptr, int32 val, char *cptr, void *desc)
{
int32 i, lnt;
t_stat r;
if (cptr == NULL) {
for (i = 0; i < hst_lnt; i++) hst[i].pc = 0;
hst_p = 0;
return SCPE_OK;
}
lnt = (int32) get_uint (cptr, 10, HIST_MAX, &r);
if ((r != SCPE_OK) || (lnt && (lnt < HIST_MIN))) return SCPE_ARG;
hst_p = 0;
if (hst_lnt) {
free (hst);
hst_lnt = 0;
hst = NULL;
}
if (lnt) {
hst = (InstHistory *) calloc (lnt, sizeof (InstHistory));
if (hst == NULL) return SCPE_MEM;
hst_lnt = lnt;
}
return SCPE_OK;
}
/* Show history */
t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, void *desc)
{
int32 ov, pf, op, k, di, lnt;
char *cptr = (char *) desc;
t_stat r;
t_value sim_eval;
InstHistory *h;
extern t_stat fprint_sym (FILE *ofile, t_addr addr, t_value *val,
UNIT *uptr, int32 sw);
if (hst_lnt == 0) return SCPE_NOFNC; /* enabled? */
if (cptr) {
lnt = (int32) get_uint (cptr, 10, hst_lnt, &r);
if ((r != SCPE_OK) || (lnt == 0)) return SCPE_ARG;
}
else lnt = hst_lnt;
di = hst_p - lnt; /* work forward */
if (di < 0) di = di + hst_lnt;
fprintf (st, "PC OV AC IO PF EA IR\n\n");
for (k = 0; k < lnt; k++) { /* print specified */
h = &hst[(++di) % hst_lnt]; /* entry pointer */
if (h->pc & HIST_PC) { /* instruction? */
ov = (h->ovac >> HIST_V_SHF) & 1; /* overflow */
pf = (h->pfio >> HIST_V_SHF) & 077; /* prog flags */
op = ((h->ir >> 13) & 037); /* get opcode */
fprintf (st, "%06o %o %06o %06o %02o ",
h->pc & AMASK, ov, h->ovac & DMASK, h->pfio & DMASK, pf);
if ((op < 032) && (op != 007)) /* mem ref instr */
fprintf (st, "%06o ", h->ea);
else fprintf (st, " ");
sim_eval = h->ir;
if ((fprint_sym (st, h->pc & AMASK, &sim_eval, &cpu_unit, SWMASK ('M'))) > 0)
fprintf (st, "(undefined) %06o", h->ir);
else if ((op < 032) && (op != 007)) /* mem ref instr */
fprintf (st, " [%06o]", h->opnd);
fputc ('\n', st); /* end line */
} /* end else instruction */
} /* end for */
return SCPE_OK;
}