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geneve: Still tuning video wait states. (nw)

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This commit is contained in:
Michael Zapf 2013-10-28 21:31:15 +00:00
parent bac6bff9e6
commit 338d3095e1
2 changed files with 51 additions and 16 deletions
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66
src/mess/machine/ti99/genboard.c
View File

@ -275,6 +275,7 @@ void geneve_mapper_device::set_wait(int min)
{
if (VERBOSE>7) LOG("genboard: Pulling down READY line for %d cycles\n", min);
m_ready(CLEAR_LINE);
m_ready_asserted = false;
}
}
@ -1064,32 +1065,64 @@ SETOFFSET_MEMBER( geneve_mapper_device::setoffset )
/*
The mapper is connected to the clock line in order to operate
the wait state counter.
The wait counter is decremented on each rising clock edge; when 0, the
READY line is asserted. However, there is a second counter which is used for
video wait states.
The READY line must be asserted when the wait counter reaches 0, but must be
cleared immediately again if the video counter has not reached 0.
(See comments at the file header: The additional video wait states do not
affect the video access itself but become effective after the access; if
the code runs on the chip, these wait states are ignored.)
*/
WRITE_LINE_MEMBER( geneve_mapper_device::clock_in )
{
if (state==ASSERT_LINE)
{
if (m_waitcount!=0)
// Rising edge
if (!m_ready_asserted)
{
m_waitcount--;
if (m_waitcount==0)
if (m_waitcount > 0)
{
if (VERBOSE>5) LOG("genboard: clock, asserting READY again\n");
m_ready(ASSERT_LINE);
m_waitcount--;
if (m_waitcount == 0)
{
if (VERBOSE>5) LOG("genboard: clock, READY asserted\n");
m_ready(ASSERT_LINE);
m_ready_asserted = true;
}
else
{
if (VERBOSE>5) LOG("genboard: clock\n");
}
}
else
{
if (m_ext_waitcount > 0)
{
m_ext_waitcount--;
if (m_ext_waitcount == 0)
{
if (VERBOSE>5) LOG("genboard: clock, READY asserted after video\n");
m_ready(ASSERT_LINE);
m_ready_asserted = true;
}
else
{
if (VERBOSE>5) LOG("genboard: vclock, ew=%d\n", m_ext_waitcount);
}
}
}
else if (VERBOSE>5) LOG("genboard: clock, still waiting %d cycle(s)\n", m_waitcount);
}
else
}
else
{
// Falling edge
// Do we have video wait states? In that case, clear the line again
if ((m_waitcount == 0) && (m_ext_waitcount > 0) && m_ready_asserted)
{
// Now for the extra video wait states
// Notice that we let the READY line get asserted before.
if (m_ext_waitcount > 0)
{
if (VERBOSE>5) LOG("genboard: clock, going for %d extra waitstates.\n", m_ext_waitcount);
m_waitcount = m_ext_waitcount;
m_ext_waitcount = 0;
m_ready(CLEAR_LINE);
}
if (VERBOSE>5) LOG("genboard: clock, READY cleared for video\n");
m_ready(CLEAR_LINE);
m_ready_asserted = false;
}
}
}
@ -1135,6 +1168,7 @@ void geneve_mapper_device::device_reset()
m_read_mode = false;
m_waitcount = 0;
m_ext_waitcount = 0;
m_ready_asserted = true;
m_geneve_mode =false;
m_direct_mode = true;

1
src/mess/machine/ti99/genboard.h
View File

@ -159,6 +159,7 @@ private:
void set_ext_wait(int min);
bool m_video_waitstates;
bool m_extra_waitstates;
bool m_ready_asserted;
bool m_read_mode;