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video/upd7220.cpp: command reset shouldn't touch RA parameters (#12905)

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Angelo Salese 2024-10-28 20:05:00 +01:00 committed by GitHub
parent 2731563334
commit 8b12c9308e
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1 changed files with 7 additions and 2 deletions
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9
src/devices/video/upd7220.cpp
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@ -1182,9 +1182,14 @@ void upd7220_device::process_fifo()
if (cr != COMMAND_RESET3)
m_de = 0;
m_ra[0] = m_ra[1] = m_ra[2] = 0;
m_ra[3] = 0x19;
// NOTE: a reset doesn't touch anything belonging to parameters, as stated in docs.
// pc9801:mightyhd won't program sad/len but just issue a reset after BIOS
// (which originally sets len = 0x1ff)
// with this on, it will len = 400 lines, repeating the bottommost two rows in a 432 setup.
//m_ra[0] = m_ra[1] = m_ra[2] = 0;
//m_ra[3] = 0x19;
m_ead = 0;
// TODO: very unlikely, should be 0xffff assuming it's even touched ...
m_mask = 0;
// FIFO, Command Processor and internal counters are cleared by this
// - pc9801rs BIOS starts up a DMAW command that spindiz2 will dislike during its boot sequences