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PDP10: Fixed TOD drift due to truncation to milliseconds.

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This commit is contained in:
Jordi Guillaumes i Pons 2014-02-25 10:47:32 +01:00
parent d0d3742504
commit 9f0261be11
1 changed files with 11 additions and 12 deletions
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21
PDP10/pdp10_tim.c
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@ -39,6 +39,7 @@
*/
#include "pdp10_defs.h"
#include <math.h>
#include <time.h>
/* The KS timer works off a 4.100 MHz (243.9024 nsec) oscillator that
@ -216,7 +217,7 @@ tempbase[0] = tim_base[0]; /* copy time base */
tempbase[1] = tim_base[1];
used = tmr_poll - (sim_activate_time (&tim_unit) - 1);
fract = (double)used / (double)tmr_poll;
fract = ((double)used) / ((double)tmr_poll);
/*
* incr is approximate number of HW ticks to add to the timebase
@ -280,21 +281,18 @@ return update_interval (tim_interval);
static t_bool update_interval (d10 new_interval)
{
/*
* The value provided is in milliseconds shifted 12 positions to the
* left; if any of the 12 rightmost bits is different to zero we must
* add one millisecond to the interval. Reference:
* The value provided is in hardware clicks. For a frequency of 4.1
* MHz, that means that dividing by 4096 (shifting 12 to the right) we get
* the aproximate value in millisenconds. If any of rhe rightmost bits is
* one, we add one unit (4096 ticks ). Reference:
* AA-H391A-TK_DECsystem-10_DECSYSTEM-20_Processor_Reference_Jun1982.pdf
* (page 4-37)
*/
int32 interval_millis = (int32)(((new_interval >> 12) +
(new_interval & TIM_HWRE_MASK ? 1 : 0)));
if (interval_millis == 0)
interval_millis = 1;
tim_new_period = new_interval & ~TIM_HWRE_MASK;
if (new_interval & TIM_HWRE_MASK) tim_new_period += 010000;
/* tim_new_period is the new value for the interval in hw ticks */
tim_new_period = interval_millis * (TIM_HW_FREQ / 1000);
/* clk_tps is the new number of clocks ticks per second */
clk_tps = 1000 / interval_millis;
clk_tps = (int32) ceil((double)TIM_HW_FREQ /(double)tim_new_period);
/* tmxr is polled every tim_mult clks. Compute the divisor matching the target. */
tim_mult = (clk_tps <= TIM_TMXR_FREQ) ? 1 : (clk_tps / TIM_TMXR_FREQ) ;
@ -320,6 +318,7 @@ static t_stat tim_svc (UNIT *uptr)
if (cpu_unit.flags & UNIT_KLAD) /* diags? */
tmr_poll = uptr->wait; /* fixed clock */
else tmr_poll = sim_rtc_calb (clk_tps); /* else calibrate */
sim_activate (uptr, tmr_poll); /* reactivate unit */
tmxr_poll = tmr_poll * tim_mult; /* set mux poll */
tim_incr_base (tim_base, tim_period); /* incr time base based on period of expired interval */