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Yamaha: don't part-modify address.

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This commit is contained in:
Thomas Harte 2023-02-11 10:35:42 -05:00
parent 7cb51c021b
commit 8e6c36bb15
1 changed files with 10 additions and 2 deletions
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12
Components/9918/Implementation/9918.cpp
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@ -911,16 +911,24 @@ void Base<personality>::write_register(uint8_t value) {
low_write_ = value;
write_phase_ = true;
// The initial write should half update the access pointer.
install_field<0>(ram_pointer_, value);
// The initial write should half update the access pointer, other than
// on the Yamaha.
if constexpr (!is_yamaha_vdp(personality)) {
install_field<0>(ram_pointer_, value);
}
return;
}
// The RAM pointer is always set on a second write, regardless of
// whether the caller is intending to enqueue a VDP operation.
// If this is a Yamaha VDP then the latched byte isn't set as part
// of the address until now.
//
// The top two bits are used to determine the type of write; only
// the lower six are actual address.
if constexpr (is_yamaha_vdp(personality)) {
install_field<0>(ram_pointer_, low_write_);
}
install_field<8, 6>(ram_pointer_, value);
write_phase_ = false;