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authorGravatarGravatar couriersud <couriersud@gmx.org>2020-07-14 05:36:06 +0200
committerGravatarGravatar couriersud <couriersud@gmx.org>2020-07-14 05:36:41 +0200
commit735752cea8c83134f3dc0046af2457d3305442ce (patch)
treea027907070b11a61165f86641f5f3e9ed8095be0
parent4cb0bd4a7a1d6e0ad0efe3d07436dedbe7c97914 (diff)
downloadmame-735752cea8c83134f3dc0046af2457d3305442ce.tar.xz
mame-735752cea8c83134f3dc0046af2457d3305442ce.zip
netlist: reduce overshoot impact on NE555 astable frequency.
If TRIG and TRESH are connected overshoot compensation will be enabled. The approach is raw but delivers results (at 5 to 10 steps per discharge/charge) within a couple of percent. Please take into account that any datasheet formulas are idealistic. Neither capacitor, resistor, internal resistor tolerances are taken into account. Nor are ambient temperature and chip temperature.
-rw-r--r--src/lib/netlist/devices/nld_ne555.cpp61
-rw-r--r--src/lib/netlist/plib/pmath.h7
2 files changed, 50 insertions, 18 deletions
diff --git a/src/lib/netlist/devices/nld_ne555.cpp b/src/lib/netlist/devices/nld_ne555.cpp
index 5cf07e2d71b..8ce5ea2a0d4 100644
--- a/src/lib/netlist/devices/nld_ne555.cpp
+++ b/src/lib/netlist/devices/nld_ne555.cpp
@@ -34,6 +34,15 @@
//- Package: DIP
//- NamingConvention: Naming conventions follow Texas instrument datasheet
//- Limitations: Internal resistor network currently fixed to 5k
+//- If TRIG and TRESH are connected overshoot compensation will be enabled.
+//- The approach is raw but delivers results (at 5 to 10 steps per discharge/charge)
+//- within a couple of percent. Please take into account that any datasheet
+//- formulas are idealistic. Neither capacitor, resistor, internal resistor
+//- tolerances are taken into account. Nor are ambient temperature and chip
+//- temperature. Thus the result is considered acceptable.
+//- The datasheet states a maximum discharge of 200mA, this is not modelled
+//- Instead an impedance of 1 Ohm is used.
+//-
//- Example: ne555_astable.c,ne555_example
//- FunctionTable:
//-
@@ -49,8 +58,10 @@
#include "netlist/analog/nlid_twoterm.h"
#include "netlist/solver/nld_solver.h"
+#include "plib/pmath.h"
+
#define R_OFF (1E20)
-#define R_ON (25) // Datasheet states a maximum discharge of 200mA, R = 5V / 0.2
+#define R_ON (1)
namespace netlist
{
@@ -71,6 +82,8 @@ namespace netlist
, m_last_out(*this, "m_last_out", false)
, m_ff(*this, "m_ff", false)
, m_last_reset(*this, "m_last_reset", false)
+ , m_overshoot(*this, "m_overshoot", 0.0)
+ , m_ovlimit(0.0)
{
register_subalias("GND", m_R3.N()); // Pin 1
register_subalias("CONT", m_R1.N()); // Pin 5
@@ -99,6 +112,10 @@ namespace netlist
m_RDIS.set_R(nlconst::magic(R_OFF));
m_last_out = true;
+ // Check for astable setup, usually TRIG AND THRES connected. Enable
+ // overshoot compensation in this case.
+ if (m_TRIG.net() == m_THRES.net())
+ m_ovlimit = nlconst::magic(0.5);
}
private:
@@ -108,41 +125,53 @@ namespace netlist
const auto reset = m_RESET();
+ const nl_fptype vthresh = clamp_hl(m_R2.P()(), nlconst::magic(0.7), nlconst::magic(1.4));
+ const nl_fptype vtrig = clamp_hl(m_R2.N()(), nlconst::magic(0.7), nlconst::magic(1.4));
+
if (!reset && m_last_reset)
{
m_ff = false;
}
else
{
- const nl_fptype vt = clamp(m_R2.P()(), nlconst::magic(0.7), nlconst::magic(1.4));
- const bool bthresh = (m_THRES() > vt);
- const bool btrig = (m_TRIG() > clamp(m_R2.N()(), nlconst::magic(0.7), nlconst::magic(1.4)));
+ const auto delta = m_THRES() + m_overshoot - vthresh;
+ const bool bthresh = (delta > 0.0);
+ const bool btrig = (m_TRIG() - m_overshoot > vtrig);
if (!btrig)
m_ff = true;
else if (bthresh)
+ {
m_ff = false;
+ }
}
const bool out = (!reset ? false : m_ff);
if (m_last_out && !out)
{
- m_RDIS.solve_now();
+ m_overshoot += ((m_THRES() - vthresh)) * 2;
+ m_overshoot = plib::clamp(m_overshoot(), nlconst::zero(), m_ovlimit);
+ m_RDIS.change_state([this]()
+ {
+ m_RDIS.set_R(nlconst::magic(R_ON));
+ });
m_OUT.push(m_R3.N()());
- m_RDIS.set_R(nlconst::magic(R_ON));
}
else if (!m_last_out && out)
{
- m_RDIS.solve_now();
+ m_overshoot += (vtrig - m_TRIG()) * 2;
+ m_overshoot = plib::clamp(m_overshoot(), nlconst::zero(), m_ovlimit);
+ m_RDIS.change_state([this]()
+ {
+ m_RDIS.set_R(nlconst::magic(R_OFF));
+ });
// FIXME: Should be delayed by 100ns
m_OUT.push(m_R1.P()());
- m_RDIS.set_R(nlconst::magic(R_OFF));
}
m_last_reset = reset;
m_last_out = out;
}
-
analog::NETLIB_SUB(R_base) m_R1;
analog::NETLIB_SUB(R_base) m_R2;
analog::NETLIB_SUB(R_base) m_R3;
@@ -157,17 +186,13 @@ namespace netlist
state_var<bool> m_last_out;
state_var<bool> m_ff;
state_var<bool> m_last_reset;
+ state_var<nl_fptype> m_overshoot;
+ nl_fptype m_ovlimit;
- nl_fptype clamp(const nl_fptype v, const nl_fptype a, const nl_fptype b)
+ nl_fptype clamp_hl(const nl_fptype v, const nl_fptype a, const nl_fptype b) noexcept
{
- nl_fptype ret = v;
- nl_fptype vcc = m_R1.P()();
-
- if (ret > vcc - a)
- ret = vcc - a;
- if (ret < b)
- ret = b;
- return ret;
+ const nl_fptype vcc = m_R1.P()();
+ return plib::clamp(v, b, vcc - a);
}
};
diff --git a/src/lib/netlist/plib/pmath.h b/src/lib/netlist/plib/pmath.h
index e70c8f7fd55..a86e3d354f1 100644
--- a/src/lib/netlist/plib/pmath.h
+++ b/src/lib/netlist/plib/pmath.h
@@ -439,6 +439,13 @@ namespace plib
return (m != 0 && n != 0) ? (plib::abs(m) / gcd(m, n)) * plib::abs(n) : 0;
}
+ template<class T>
+ constexpr const T& clamp( const T& v, const T& low, const T& high)
+ {
+ gsl_Expects(high >= low);
+ return (v < low) ? low : (high < v) ? high : v;
+ }
+
static_assert(noexcept(constants<double>::one()), "Not evaluated as constexpr");
} // namespace plib